The selection of Judge Barrett, a deeply conservative jurist, kicked off an election-season confirmation fight unlike any in American history. The Senate Judiciary Committee will begin hearings on Oct. 12.

At a Pennsylvania rally, Trump says he’d have an edge if the 2020 race is decided by Congress.

President Trump announced Saturday afternoon that he would nominate Judge Amy Coney Barrett to the Supreme Court, setting off a politically explosive scramble to confirm a deeply conservative jurist before Election Day.

“Today it is my honor to nominate one of our nation’s most brilliant and gifted legal minds to the Supreme Court,” Mr. Trump said. “She is a woman of unparalleled achievement, towering intellect, sterling credentials and unyielding loyalty to the Constitution.”

Mr. Trump introduced Judge Barrett, a former Notre Dame law professor who now sits on a federal appeals court in Chicago and is a favorite of anti-abortion activists, at a ceremony in the White House Rose Garden. The event came just a little over a week after the death of Justice Ruth Bader Ginsburg.

Mr. Trump noted that Judge Barrett graduated first in her class at Notre Dame Law School and served as a clerk for Justice Antonin Scalia, a job Mr. Trump called “one of the highest honors a young lawyer could have.”

In her own remarks, Judge Barrett said she was “deeply honored” and that, if confirmed, she would serve in the model of her former boss, who died in 2016.

“His judicial philosophy is mine, too,” she said of Justice Scalia. “A judge must apply the law as written. Judges are not policymakers, and they must be resolute in setting aside any policy views they may hold.”

Judge Barrett’s confirmation would cement a 6-to-3 conservative majority on the court, leaving an imprint that could long outlast Mr. Trump’s presidency. The nomination is expected to consume the Senate in the weeks ahead and quickly reverberate on the campaign trail, injecting polarizing issues like abortion rights into an election season already weighed down by the coronavirus pandemic and a national reckoning over racism.

Senate Republicans have vowed to confirm the president’s nominee with haste and are preparing to oversee a lightning-fast confirmation process that could put her on the bench before Nov. 3. It would be a historic feat: No justice has ever been confirmed so close to an election, and in this case, voters in some states are already casting ballots.

Democrats, still furious over Republicans’ outright refusal to consider President Barack Obama’s nominee to the court in 2016, have argued that they have no right to fill the seat so close to the election. But locked in the minority, they are largely powerless to stop it. The Democrats intend to use the fight to stoke outrage about the possible loss of abortion rights and the Affordable Care Act, both of which could come under threat with Judge Barrett on the court. They hope it can help them reclaim the presidency and the Senate majority.

Of the confirmation process, Mr. Trump said with sarcasm, “I’m sure it’ll be extremely noncontroversial.” He added, alluding to the contentious confirmation process for Justice Brett M. Kavanaugh, “We said that the last time, didn’t we?”

Later Saturday, he told reporters before leaving for a rally in Middletown, Pa., “I think this will be done before the election.”

Judge Barrett is in many ways the ideological opposite of Justice Ginsburg, who led the court’s liberal wing. She has an unwaveringly conservative voting record in cases that touch on abortion, gun rights, discrimination and immigration. At 48, she would be the youngest justice on the court, with the potential to shape the law for decades to come.

“Should I be confirmed, I will be mindful of who came before me,” Judge Barrett said, paying tribute to Justice Ginsburg: “She not only broke glass ceilings, she smashed them, and for that she has won the admiration of women across the country.”

Mr. Trump noted that if Judge Barrett is confirmed, she will be the first mother of school-age children to sit on the bench. There have been male justices with school-age children, as well.

“Amy is more than a stellar scholar and judge,” he said. “She’s also a profoundly devoted mother.”

Senator Mitch McConnell of Kentucky, the Republican majority leader, has already vowed that the Senate will vote on President Trump’s Supreme Court nominee by the end of the year, though he has not made clear whether that will happen before Election Day, Nov. 3.

Now that Mr. Trump has announced his selection of Judge Amy Coney Barrett for the court’s open seat, what comes next? Here are some of the crucial questions to determine how it will play out.

What happens next? Judge Barrett will have to answer an elaborate questionnaire, which the Senate will examine. She’ll also begin calling and meeting with senators as they scrub her background and legal writings.

The 22 members of the Judiciary Committee, which is led by Senator Lindsey Graham of South Carolina, a staunch Trump ally, will hold confirmation hearings for four consecutive days beginning Oct. 12. That is considerably faster than recent Supreme Court nominations, cutting the time to prepare for the hearings by about two-thirds.

After the hearings, the committee will vote on whether to recommend the nomination to the full Senate, a meeting Republicans have tentatively scheduled for Oct. 22. If that schedule holds, the full Senate would vote on whether to confirm Judge Barrett the final week of October, just a week before Election Day.

Because Republicans hold a 53 to 47 majority, Democrats would need four Republican senators to join them in opposition to sink Judge Barrett.

Two Republicans, Susan Collins of Maine and Lisa Murkowski of Alaska, had said they opposed filling the seat until voters decide the presidency. Ms. Collins has stood by that view, warning that she will not vote to confirm Mr. Trump’s nominee before Election Day, period. Ms. Murkowski now appears more open to doing so, but as a vocal proponent of abortion rights, she is expected to look warily on Judge Barrett.

All 51 other Republicans so far appear to be content with the nominee, and given their eagerness to fill the vacancy with a conservative and the tight timetable, they are going to be hesitant to break with their party leaders.

Democrats eliminated the 60-vote threshold for most judicial nominees in 2013, frustrated by Republicans’ use of the filibuster to slow and impede President Barack Obama’s agenda. In turn, angered by resistance to the nomination of Justice Neil M. Gorsuch in 2017, Republicans abolished the limitation on Supreme Court nominees.

As a result, Mr. McConnell could bring the nomination to the Senate floor and approve it with a simple majority vote.

What effect will the election have on the vacancy? For many Republican senators up for re-election this year, the ideal situation might be to begin the confirmation process quickly, injecting it into the political bloodstream and energizing conservative voters, but waiting until after Election Day — when vulnerable incumbents no longer have to worry about being cast out by angry independent and liberal voters — to hold a confirmation vote.

What if Republicans lose the White House, the Senate or both? Could they still confirm Mr. Trump’s nominee after the election? Yes.

Congress typically reconvenes after Election Day for a lame-duck session, when lawmakers act on unfinished business before adjourning for the year. Since the newly elected members would not be seated until the new Congress convened in January, Republicans would remain in control of the Senate even if they had lost their majority.

Similarly, if he were to lose on Election Day, Mr. Trump would remain president until Joseph R. Biden Jr. assumed office in January.

Pressing his case that the November election will be a “disaster,” President Trump told supporters on Saturday night that he hoped any dispute over the vote tally would not have to be decided by Congress — but that he would have an advantage if it did.

“I don’t want to end up in the Supreme Court and I don’t want to go back to Congress either, even though we have an advantage if we go back to Congress,” Mr. Trump said at a rally in Middletown, Pa. “Does everyone understand that? I think it’s 26 to 22 or something, because it’s counted as one vote per state. So we actually have an advantage.”

Mr. Trump appeared to be referring to what is known as a contingent election, in which the House of Representatives chooses the next president if no candidate wins an absolute majority of votes in the Electoral College. In that scenario, each state’s House delegation is given one vote, with 26 votes required to win. Mr. Trump was correct that Republicans currently control 26 state delegations and Democrats 22, with two effectively tied — although the vote occurs after a new Congress is seated in early January, so those totals could change. (The Senate would separately choose the vice president.)

Mr. Trump is also hoping that a pre-election Senate confirmation of his choice for the Supreme Court, Judge Amy Coney Barrett, will guarantee him a conservative majority on the high court in the event that it decides the outcome, as it did in 2000.

Hours after announcing Judge Barrett’s nomination, Mr. Trump spoke in light rain to an outdoor crowd of perhaps a few thousand — far fewer than the “tens of thousands” he claimed from onstage — on an airport tarmac near Harrisburg. It was the latest of several rallies he has held in which his supporters have packed together closely despite the pandemic, mostly without masks.

Flanked by a huge television screen with the words “Fill that seat,” Mr. Trump drew roars of applause and chants of “U.S.A.” when he predicted that Republicans in the Senate would quickly confirm Judge Barrett.

As has become his routine, Mr. Trump again cast doubt on the reliability of mail-in ballots and claimed without evidence that Democrats were plotting to use them to steal the November election from him.

“Keep your eyes open,” he told supporters, urging them to watch for “any shenanigans” like “people dumping things, flushing things.”

Mr. Trump lavished praise on Judge Barrett, calling her “a brilliant legal mind and extraordinary scholar.”

“That’s a little better than Biden, wouldn’t you say,” he asked, referring to his Democratic opponent, Joseph R. Biden Jr.

President Trump’s announcement that he would nominate Judge Amy Coney Barrett to the Supreme Court immediately set off an intense partisan fight over her confirmation, with Republicans enthusiastically praising the judge for her sterling legal credentials and Democrats warning that she would dismantle health care protections and abortion rights.

Senator Mitch McConnell, the majority leader, said Mr. Trump “could not have made a better decision.” He vowed again that Judge Barrett would receive a vote on the Senate floor “in the weeks ahead,” after her nomination is reviewed by the Judiciary Committee.

“Judge Amy Coney Barrett is an exceptionally impressive jurist and an exceedingly well qualified nominee to the Supreme Court of the United States,” Mr. McConnell, Republican of Kentucky, said in a statement.

He said the Senate would evaluate the nomination on the basis of Judge Barrett’s “objective qualifications.”

“But it cannot escape notice that this nominee has also already won national admiration for her shining example of strong female leadership at the very top of her field,” Mr. McConnell added. “As our nation continues to mourn Justice Ginsburg and honor her trailblazing legacy, it does seem fitting that another brilliant and talented woman at the height of their shared profession would follow in her footsteps onto the court.”

Senator Chuck Schumer, the minority leader, wasted no time saying he would fight the nomination. He accused Mr. Trump and the Senate Republicans of “shamelessly rushing to fill Justice Ginsburg’s seat less than 40 days before a presidential election.”

“The American people should make no mistake — a vote by any senator for Judge Amy Coney Barrett is a vote to strike down the Affordable Care Act and eliminate protections for millions of Americans with pre-existing conditions,” Mr. Schumer, Democrat of New York, said in a statement.

Mr. Schumer said Judge Barrett’s record “also makes clear that if she is confirmed, the reproductive freedoms that millions of women hold dear would be in grave danger.”

Several Democrats — including Senators Jeff Merkley of Oregon and Richard Blumenthal of Connecticut — said they would not meet with Judge Barrett before her confirmation hearings.

“This is an illegitimate nomination,” Mr. Merkley told Politico. “I personally have no desire to pretend it’s acceptable.”

Senator Lindsey Graham, Republican of South Carolina and the chairman of the Judiciary Committee, said he was committed to giving Judge Barrett “a challenging, fair, and respectful hearing,” even as he called her “highly qualified in all the areas that matter — character, integrity, intellect, and judicial disposition.”

At least one moderate Republican, Senator Lisa Murkowski of Alaska, did not say if she considered Judge Barrett a qualified nominee. She said only that she would meet with the judge, just as she had with Judge Merrick B. Garland, President Barack Obama’s nominee to the Supreme Court who was blocked by Senate Republicans four years ago.

“For weeks I have stated that I do not support taking up a potential Supreme Court vacancy this close to an election,” Ms. Murkowski said. “But today the president exercised his constitutional authority to nominate an individual to fill the vacancy on the Supreme Court left by the passing of Justice Ruth Bader Ginsburg. I welcome the opportunity to meet with the Supreme Court nominee, just as I did in 2016.”

Senator Susan Collins of Maine, another moderate Republican, said in a statement: “In the interest of both fairness to the American people and consistency in following the practice established four years ago, there should not be a vote on a Supreme Court nominee prior to the election. As I stated even before Justice Ginsburg’s death, should a nominee for the Supreme Court be brought to the Senate floor before the election, I will vote no.”

Senator Mitt Romney of Utah, whose support for a vote on the nomination helped give Republicans the support they needed to fill the seat, called Judge Barrett a “highly respected jurist with distinguished legal and academic credentials.”

“I believe our next justice must faithfully apply the law and our Constitution, impartially and regardless of policy preferences,” he said on Twitter.

Joseph R. Biden Jr. criticized President Trump’s decision to nominate Judge Amy Coney Barrett to the Supreme Court on Saturday, arguing that she would overturn vital health care protections for Americans in the middle of the coronavirus pandemic.

“Today, President Trump has nominated Judge Amy Coney Barrett as the successor to Justice Ginsburg’s seat,” Mr. Biden said in a statement. “She has a written track record of disagreeing with the U.S. Supreme Court’s decision upholding the Affordable Care Act. She critiqued Chief Justice John Roberts’ majority opinion upholding the law in 2012.”

Mr. Biden, the Democratic presidential nominee, linked the nomination to Mr. Trump’s effort over the last four years to “throw out” the Affordable Care Act, the Obama administration’s signature health care law. He noted that the Supreme Court will hear arguments on the latest challenge to the Affordable Care Act a week after Election Day, on Nov. 10.

“If President Trump has his way, complications from Covid-19, like lung scarring and heart damage, could become the next deniable pre-existing condition,” Mr. Biden said.

Although Republicans have vowed to move swiftly on Judge Barrett’s nomination, Mr. Biden said the Senate should not fill the vacancy until after Election Day on Nov. 3.

“The United States Constitution was designed to give the voters one chance to have their voice heard on who serves on the court,” he said. “That moment is now and their voice should be heard.”

Writing on Twitter, Mr. Biden urged Americans to “vote like your health care is on the ballot — because it is.”

For Joseph R. Biden Jr. and the Democratic Party that he now leads, the selection of Judge Amy Coney Barrett by President Trump on Saturday puts a name and a face to the urgent threat they believe a 6-3 conservative majority on the Supreme Court poses to decades of progressive laws and protections.

Instead, Democrats pressing to slow or stop the advancement of Mr. Trump’s pick are determined to frame the debate around the real-world consequences — especially on health care but also on abortion — of what would be the biggest ideological swing since Justice Clarence Thomas replaced the late Justice Thurgood Marshall.

For Mr. Trump, the choice of Judge Barrett represents a welcome chance to shake up a race in which he has been trailing in the polls, and potentially address a staggering gender gap by shoring up his standing with more conservative women who are alienated by his personal style and other elements of his record.

It also provides him with something of a leading woman as part of his 2020 ticket, and a ferocious confirmation battle that could shift some national attention away from a pandemic that has cost the lives of more than 200,000 Americans and toward the kind of culture war turf that Mr. Trump is most comfortable occupying.

A majority of Americans believe the winner of the November election should make the pick, according to recent polling. But in nominating Judge Barrett to replace Justice Ruth Bader Ginsburg, Mr. Trump has pushed to the forefront a complex new stew of factors as Republicans play up her personal story as an accomplished 48-year-old working mother of faith. It’s a development that could sway or mobilize key voting blocs on both sides of the aisle: evangelical and conservative Catholic voters, abortion-rights activists and opponents, women and young people.

All of those political crosscurrents will be on display on Tuesday, as Mr. Trump and Mr. Biden head into the first debate of the general election. A sizable share of the waning days of the campaign will be consumed by the court fight: Just the committee hearings and a final confirmation vote alone would account for more than 10 percent of the remaining calendar.

“It’s a little bit of a tricky balance Democrats are going to have to think through,” said Dan Sena, a Democratic strategist who oversaw the party’s takeover of the House of Representatives in 2018.

“Your base is going to want you to stand up and fight for a seat basically viewed as a Democratic-leaning seat,” Mr. Sena added. But depending on how the battle unfolds, he warned, it may “put people in hyperpartisan corners,” which could endanger Democratic gains with swing voters.

“Today, it is my honor to nominate one of our nation’s most brilliant and gifted legal minds to the Supreme Court. She is a woman of unparalleled achievement, towering intellect, sterling credentials and unyielding loyalty to the Constitution: Judge Amy Coney Barrett.” [Applause] “The flag of the United States is still flying at half staff in memory of Justice Ruth Bader Ginsburg, to mark the end of a great American life. Justice Ginsburg began her career at a time when women were not welcome in the legal profession. But she not only broke glass ceilings, she smashed them. For that, she has won the admiration of women across the country, and indeed all over the world.” [Applause] “She was a woman of enormous talent and consequence, and her life of public service serves as an example to us all. Particularly poignant to me, was her long, and deep friendship with Justice Antonin Scalia, my own mentor. I clerked for Justice Scalia more than 20 years ago. But the lessons I learned still resonate. His judicial philosophy is mine, too: A judge must apply the law as written. Judges are not policymakers, and they must be resolute in setting aside any policy views they might hold. If confirmed, I would not assume that role for the sake of those in my own circle, and certainly not for my own sake. I would assume this role to serve you. I would discharge the judicial oath, which requires me to administer justice without respect to persons, do equal right to the poor and rich, and faithfully and impartially discharge my duties under the United States Constitution.”

Judge Amy Coney Barrett, President Trump’s pick for the Supreme Court, has compiled an almost uniformly conservative voting record in cases touching on abortion, gun rights, discrimination and immigration. If she is confirmed, she would move the court slightly but firmly to the right, making compromise less likely and putting at risk the right to abortion established in Roe v. Wade.

Judge Barrett’s judicial opinions, based on a substantial sample of the hundreds of cases that she has considered in her three years on the federal appeals court in Chicago, are marked by care, clarity and a commitment to the interpretive methods used by Justice Antonin Scalia, the giant of conservative jurisprudence for whom she worked as a law clerk from 1998 to 1999.

But while Justice Scalia’s methods occasionally drove him to liberal results, notably in cases on flag burning and the role of juries in criminal cases, Judge Barrett could be a different sort of justice.

“There may be fewer surprises from someone like her than there were from Justice Scalia,” said Brian T. Fitzpatrick, a former law clerk to the justice and a law professor at Vanderbilt University. “She is sympathetic to Justice Scalia’s methods, but I don’t get the sense that she is going to be a philosophical leader on how those methods should be executed.”

One area in which almost no one expects surprises is abortion. Mr. Trump has vowed to appoint justices ready to overrule Roe v. Wade, the 1973 decision that established a constitutional right to abortion. Groups opposing abortion have championed Judge Barrett’s nomination. And her academic and judicial writings have been skeptical of broad interpretations of abortion rights.

Judge Barrett will doubtless tell senators that the Roe decision is a settled precedent, as she did when Mr. Trump nominated her to the appeals court in 2017. And the Supreme Court may not hear a direct challenge to Roe anytime soon, preferring instead to consider cases that could chip away at abortion rights.

But when the day comes, many of Judge Barrett’s supporters are convinced that she will not flinch. Justice Scalia wrote that the Constitution has nothing to say about abortion and that states should be allowed to decide the question for themselves. There is no reason to believe Judge Barrett disagrees.

Judge Amy Coney Barrett spoke on Saturday after President Trump announced that he would nominate her to the Supreme Court. The following are some highlights of her remarks.

“The flag of the United States is still flying at half-staff, in memory of Justice Ruth Bader Ginsburg, to mark the end of a great American life. Justice Ginsburg began her career at a time when women were not welcome in the legal profession. But she not only broke glass ceilings, she smashed them. For that, she has won the admiration of women across the country and indeed, all over the world. She was a woman of enormous talent and consequence and her life of public service serves as an example to us all.”

“Particularly poignant to me was her long and deep friendship with Justice Antonin Scalia, my own mentor. Justices Scalia and Ginsburg disagreed fiercely in print without rancor in person. Their ability to maintain a warm and rich friendship despite their differences even inspired an opera. These two great Americans demonstrated that arguments, even about matters of great consequence, need not destroy affection.”

“I clerked for Justice Scalia more than 20 years ago, but the lessons I learned still resonate. His judicial philosophy is mine, too. A judge must apply the law as written. Judges are not policymakers and they must be resolute in setting aside any policy views they might hold.”

“I could not manage this very full life without the unwavering support of my husband, Jesse. At the start of our marriage, I imagined that we would run our household as partners. As it has turned out, Jesse does far more than his share of the work. To my chagrin, I learned at dinner recently that my children consider him to be the better cook. For 21 years, Jesse has asked me every single morning what he can do for me that day. And though I almost always say, ‘Nothing,’ he still finds ways to take things off my plate. And that’s not because he has a lot of free time. He has a busy law practice. It is because he is a superb and generous husband and I am very fortunate.”

“I have no illusions that the road ahead of me will be easy, either for the short term or the long haul. I never imagined that I would find myself in this position. But now that I am, I assure you that I will meet the challenge with both humility and courage. Members of the United States Senate, I look forward to working with you during the confirmation process. And I will do my very best to demonstrate that I am worthy of your support.”

“You are controversial. Let’s start with that — you’re controversial because many of us that have lived our lives as women really recognize the value of finally being able to control our reproductive systems, and Roe entered into that obviously. I listened to your answers to Senator Grassley’s question, and it leaves me a bit puzzled because you have a long history of believing that your religious beliefs should prevail.” “How do you evaluate the precedents, plural, with respect to Roe?” “The Supreme Court precedents?” “Yes.” “Well, Roe and Casey and its progeny, as you say, Roe has been affirmed many times and survived many challenges in the court. And it’s more than 40 years old, and it’s clearly binding on all courts of appeals. And so it’s not open to me or up to me and I would have no interest in, as a Court of Appeals Judge, challenging that precedent. It would bind.” “Why is it that so many of us on this side have this very uncomfortable feeling that, you know, dogma and law are two different things. And I think whatever a religion is, it has its own dogma. The law is totally different. And I think in your case, professor, when you read your speeches, the conclusion one draws is that the dogma lives loudly within you. And that’s of concern when you come to big issues that large numbers of people have fought for years in this country.”

As President Trump moves ahead with his Supreme Court nominee, and Senate Republicans prepare to hold lightning-quick confirmation hearings ahead of the election, they are making risky calculations aimed at navigating difficult political straits with less than 40 days left in the campaign.

In order to achieve a new 6-to-3 conservative majority on the court, Republicans are poised to defy a clear majority of voters who have indicated in polls that they want the winner of the election to pick a nominee for Justice Ruth Bader Ginsburg’s seat. They are even willing to energize Democratic turnout in the short run by elevating issues like abortion, if it means achieving the long-term goal of tilting the court further to the right.

Now, though, Mr. Trump’s advisers and party lawmakers are placing wagers on Mr. Trump’s pick, Judge Amy Coney Barrett. It is a gamble based on hope as much as strategy, as Mr. Trump trails in battleground states and the Senate G.O.P. majority appears increasingly precarious.

They believe a partisan fight over the court offers them at least a chance to steer the debate away from political danger zones like the president’s handling of the pandemic and his unceasing rhetorical eruptions, most recently his indication that he would be unwilling to agree to a peaceful transition of power.

“Either the election can be about Trump or about Covid or about the Supreme Court,” said Senator Lamar Alexander, the long-serving Tennessee Republican who is retiring next year.

If Republicans are skeptical that they can retain the presidency and the Senate in any election that is a referendum on Mr. Trump’s leadership, they are betting that Democrats will botch the confirmation process with ferocious attacks that makes his nominee a sympathetic figure.

On this, Republicans say, they have history on their side, as they point to the bitter 2018 fight over Justice Brett M. Kavanaugh that resulted in the party’s adding to its Senate majority.

During her Court of Appeals confirmation hearing in 2017, a remark from Senator Dianne Feinstein became a badge of defiance for conservatives battling what they saw as anti-religion bias by Democratic lawmakers.

Asked whether her Roman Catholic faith would influence her decisions on the bench, Judge Barrett told the senators that she was a faithful Catholic, and that her religious beliefs would not affect her decisions as an appellate judge.

Some Republicans are already calling Judge Amy Coney Barrett the Notorious A.C.B. and sharing images of her with a crown on her head. And some fans of Justice Ruth Bader Ginsburg, a.ka. the Notorious R.B.G., are incensed.

On Saturday, just after President Trump announced Judge Barrett as his nominee to fill Justice Ginsburg’s seat on the Supreme Court, the National Republican Senatorial Committee began selling T-shirts with a design ripped directly from the meme that helped make Justice Ginsburg a pop culture icon and hero to many young people, as the Notorious R.B.G.

Of course, the R.B.G. name itself was a play on the Notorious B.I.G., the famous rapper who was born in Brooklyn, like Justice Ginsburg.

“ACB is a BIG upgrade from RBG,” Representative Doug Collins, Republican of Georgia, wrote on Twitter along with an image of Judge Barrett as the Notorious A.C.B. with a crown on her head.

“This is the nadir of creative bankruptcy,” said one Twitter user, Brooke Binkowski. “Just no new ideas whatsoever lol.”

Chris D. Jackson, a county commissioner in Tennessee, said on Twitter that conservatives who have called Judge Barrett A.C.B. “make me sick.”

The comedian Andy Richter also panned the Notorious A.C.B. T-shirt. “The person that thought of this was wearing pleated pants,” he wrote.

In choosing Amy Coney Barrett, a conservative and a hero to the anti-abortion movement, as his nominee to the Supreme Court, President Trump has found the polar opposite of Justice Ruth Bader Ginsburg, a champion of reproductive rights and leader of the liberal wing of the court.

Judge Barrett has been on the bench for only three years, appointed by Mr. Trump to the United States Court of Appeals for the Seventh Circuit in 2017. On Friday, opponents of the nomination criticized the Trump administration for rushing the process and said that Judge Barrett, if confirmed, would vote to restrict access to abortion, gut the Affordable Care Act and reverse progress on marriage equality.

“It’s no surprise Trump would want to nominate Amy Coney Barrett, a judge with a track record of anti-L.G.B.T.Q. rhetoric,” the Human Rights Campaign, a prominent lesbian, gay, bisexual, transgender and queer advocacy group, said in a tweet on Friday. “She’s argued against trans rights, marriage equality and reproductive rights — and she shouldn’t be on the Supreme Court.”

Judge Barrett, a Catholic jurist with solid anti-abortion credentials, is a popular figure among conservative Catholics and other Christians, and some supporters have sought to frame the opposition to her nomination as an attack on her religious beliefs.

“It’s go time!” Kristan Hawkins, the president of the anti-abortion group Students for Life, tweeted on Friday. “Get ready for a post Roe v Wade America!” The March for Life called Judge Barrett “an excellent choice” and “exactly the trailblazer we want to see on the court.”

It’s go time! Get ready for a post Roe v Wade America! #ProLifeGen Assemble! This is what we were made for and have been preparing for!

While it is possible that the nomination could energize Democratic opposition amid a presidential campaign, Michael Steele, a former chairman of the Republican National Committee, said in an appearance on MSNBC that Mr. Trump’s choice could improve his chances of re-election.

“This pick helps,” he said of the president’s campaign. “I think the Biden campaign and the Democrats need to be smart about how they approach this nominee.”

In a tweet on Friday, Senator John Cornyn, Republican of Texas, called Judge Barrett “a legal trailblazer” who respected the country’s founding principles.

People close to Judge Barrett have already begun to fill out a biographical portrait of her ahead of the confirmation process in the Senate.

They believe that many of the establishment conservative groups already know her bona fides, according to a person briefed on the strategy. So now, as people across the country get to know the relatively obscure judge from Indiana, they are trying to highlight her work as a professor, her engagement with students and her years as a working mother.

Her allies are pushing for pieces about her in national publications that show her in a favorable light in the hopes that they avoid her becoming caricatured as too extreme by Democrats who are opposed to her nomination based on rulings that she has made on a number of issues.

The Judicial Crisis Network, a conservative group, said on Saturday that it was beginning a $3 million ad campaign in support of the nomination. The group’s ad will air on cable and in states including Colorado, Iowa, Maine, North Carolina and Utah, as well as Washington, D.C. It says Judge Barrett “ignores politics,” is “grounded in faith and family” and is “the perfect choice to follow Justice Ginsburg.”

With President Trump’s selection of Judge Amy Coney Barrett to fill Justice Ruth Bader Ginsburg’s Supreme Court seat, a partisan battle will ensue. That battle is what Mr. Trump, who is losing to Joseph R. Biden Jr. in nearly every public poll, is pinning his hopes on for a change in the arc of the 2020 race.

Judge Barrett, 48, whom Mr. Trump considered in 2018 to replace the retiring Justice Anthony Kennedy, fits the mold of the type of candidate who the president believes will appeal to his conservative base.

That does not mean Mr. Trump’s calculation is right. Several people close to the process said that Mr. Trump did not listen to advice from several people that he consider a judge in Florida, Barbara Lagoa, who was confirmed on a bipartisan vote and who could appeal to the Latino voters the president needs.

But what Judge Barrett does is satisfy the evangelical supporters whose admiration the president craves, and whom Mr. Trump has feared losing throughout his term.

And so begins weeks of debate over the nominee in an election in which Mr. Trump has dwindling chances to change the dynamics.

After a half-century in public life, with a lead role in several indelible confirmation dramas through the years, Joseph R. Biden Jr. could, if elected, be saddled with a Supreme Court primed to counteract his policy aims on health care, abortion and other defining issues.

Many Democrats now believe that adding seats to the court is the urgent remedy, an extraordinary step that has not been seriously contemplated since the administration of Franklin D. Roosevelt. They argue that the court’s legitimacy has already eroded amid the Republican confirmation maneuvers of the last four years.

Yet for Mr. Biden, a proud man of the Senate, such an effort would amount to the sort of norm-razing exercise that might strike him as an escalation too many.

“My inclination is to think that he would just see that as making it more political instead of making it less political,” said Cynthia C. Hogan, a former Judiciary Committee aide who helped lead Mr. Biden’s search for a 2020 running mate. “I think he wants to restore the court to its earlier place of respect.”

The court has unavoidably moved to the center of the campaign, with President Trump’s announcement on Saturday that he is nominating Judge Amy Coney Barrett, a favorite of conservatives, to replace Justice Ruth Bader Ginsburg.

If the judiciary is a subject with which Mr. Biden is intimately familiar — perhaps more so than any modern nominee — it is also one that he has largely avoided in the presidential race, preferring to focus on the calamitous federal response to the coronavirus pandemic and the perpetual volatility of Mr. Trump’s rule.

The broader irony is not lost on Mr. Biden’s allies: He is, at present, effectively powerless to stop the ideological drift of a court wrenched to the right by a president who ran casinos when Mr. Biden ran the Senate Judiciary Committee.

And even if Mr. Biden is elected, his institutionalist bearing might preclude his support for a possible workaround.

Interviews with more than a dozen former colleagues, aides and other contemporaries from his earlier court clashes present Mr. Biden as a conflicted combatant in the judicial trenches, negotiating the constant tug between precedent and pragmatism, convention and conviction.

Alisa Anderson, a lifelong Catholic from Livonia, Mich., does not typically give much weight to the religious backgrounds of political candidates. But the deeply personal way Joseph R. Biden Jr. discusses his Catholicism has caught her attention.

“Biden has shown us that his faith has led him through some very dark times and I have admiration for someone who can admit that,” Ms. Anderson, 57, who is leaning toward Mr. Biden, said in a recent interview. “Trump has never made mention of his faith, unless it’s for political gain.”

That doesn’t bother Nathan Sullivan, a 29-year-old from Tucson, Ariz. For observant Catholics like him, the motive matters less than the results Mr. Trump achieves on issues like abortion.

“He’s a person of action,” said Mr. Sullivan, who voted for Mr. Trump in 2016 and will do so again this time, citing abortion as his most important issue. “I care a lot more about what he does than what he believes.”

Those two perspectives, from two critical swing states, shed light on the radically different appeal Mr. Biden and Mr. Trump hold for American Catholics, a diverse constituency that includes some of the few swing voters left.

Those voters are likely to receive significant attention in the coming weeks now that Mr. Trump has settled on Amy Coney Barrett, a federal appeals court judge with a deeply conservative judicial record, as his choice to replace Justice Ruth Bader Ginsburg on the Supreme Court.

In recent years, the majority of white Catholics have leaned Republican and Hispanic Catholics tilted Democratic. This year, even as Mr. Trump trails in many polls, each campaign sees opportunities to reduce the other’s margins with Catholic voters — enough, they hope, to tip key states their way.

Mr. Biden and Mr. Trump have vastly different political bases, but both are battling over more conservative, religious Latinos in places like Florida and Arizona.

They are also targeting a segment of persuadable white Catholics in the industrial Midwest — in particular, blue-collar, union households in places like Wisconsin and Michigan. It’s a more competitive voting group than the white evangelicals who are among Mr. Trump’s most loyal supporters, and some polls in recent months have offered signs of erosion in the president’s advantage with white Catholics compared with 2016, when they favored him by about two to one.

“If you’re looking in the religious landscape for something that looks like a possible swing constituency, it’s a group Trump won strongly in ’16,” said Robert P. Jones, an author and the chief executive of the Public Religion Research Institute. “If I’m the Trump administration, I’m less worried about the white evangelical vote. I’d be deeply worried about where white Catholics are.”

When Justice Ruth Bader Ginsburg joined President Barack Obama for lunch in his private dining room in July 2013, the White House sought to keep the event quiet — the meeting called for discretion.

Mr. Obama had asked his White House counsel, Kathryn Ruemmler, to set up the lunch so he could build a closer rapport with the justice, according to two people briefed on the conversation. Treading cautiously, he did not directly bring up the subject of retirement to Justice Ginsburg, at 80 the Supreme Court’s oldest member and a two-time cancer patient.

He did, however, raise the looming 2014 midterm elections and how Democrats might lose control of the Senate. Implicit in that conversation was the concern motivating his lunch invitation — the possibility that if the Senate flipped, he would lose a chance to appoint a younger, liberal judge who could hold on to the seat for decades.

But the effort did not work, just as an earlier attempt by Senator Patrick Leahy, the Vermont Democrat who was then Judiciary Committee chairman, had failed. Justice Ginsburg left Mr. Obama with the clear impression that she was committed to continuing her work on the court, according to those briefed.

In an interview a year later, Justice Ginsburg deflected questions about the purpose of the lunch. Pressed on what Mr. Obama might think about her potential retirement, she said only, “I think he would agree with me that it’s a question for my own good judgment.”

With Justice Ginsburg’s death last week, Democrats are in a major political battle, as Republicans race to fill her seat and cement the court’s conservative tilt.

Mr. Obama clearly felt compelled to try to avoid just such a scenario, but the art of maneuvering justices off the court is politically delicate and psychologically complicated. They have lifetime appointments and enjoy tremendous power and status, which can be difficult to give up.

Still, presidents throughout American history have strategized to influence the timing of justices’ exits to suit various White House priorities.

Many voting rules have changed this year because of the pandemic, making it harder than usual to figure out how to cast your ballot. So we did the work for you, in hopes of helping to make sure your vote is counted.

Many rules have changed during the pandemic, so this interactive guide can help you ensure your vote is counted.

A crucial stretch of the race is about to start as President Trump announces Amy Coney Barrett as Supreme Court nominee and the first debate looms. Read the latest.

Many rules have changed during the pandemic, making it harder to figure out how to cast your ballot. This interactive guide can help you ensure your vote is counted.

Joe Biden and Donald Trump need 270 electoral votes to reach the White House. Try building your own coalition of battleground states to see potential outcomes.


News – Confirmation Battle Looms as Trump Picks Barrett for Supreme Court