Joe Biden and Donald Trump will bring very different histories and styles to their presidential debate on Tuesday.

Donald J. Trump barely paused to thank his debate hosts before going on the attack after he took the stage at Hofstra University in September 2016. “Our jobs are fleeing the country,” he said grimly. “They’re going to Mexico.”

For the next 90 minutes — and over the course of his two other debates with Hillary Clinton, his Democratic opponent — Mr. Trump displayed a relentless and disciplined debate style, at times bulldozing Mrs. Clinton and the debate moderators. Though many observers considered Mrs. Clinton the clear winner in the debates, Mr. Trump’s defiant attacks on Washington and his argument that the system was stacked against ordinary Americans resonated with angry and alienated voters and helped lead to his unexpected victory.

Joseph R. Biden Jr., the Democratic presidential candidate who will meet Mr. Trump on a debate stage for the first time on Tuesday night, was certainly not as aggressive when, as vice president, he debated his Republican opponent, Representative Paul Ryan of Wisconsin, in October 2012. But Mr. Biden used a command of foreign policy, Congress and the White House to hammer and at times belittle his rival and turn back attacks on President Barack Obama.

“With all due respect, that’s a bunch of malarkey,” he said, in the kind of conversational turn of phrase he has invoked throughout his career, when Mr. Ryan accused the administration of mishandling the deadly terrorist attack on American diplomats in Benghazi, Libya.

For both Mr. Trump and Mr. Biden, the three presidential debates may well be the most critical moments of a fall campaign that is being carried out without the typical dawn-to-dusk days of rallies, local television appearances and talking to voters. Millions of Americans will set aside time in the midst of a pandemic to judge Mr. Trump and Mr. Biden side by side in the unfiltered forum of the two men on a stage.

Through 14 primary and general election debates in 2015 and 2016, Mr. Trump emerged as the showman, with a keen sense on how to seize the spotlight, hammer home clear and succinct themes and discombobulate an opponent with claims and accusations that, while often false, are difficult to rebut in real time.

By contrast, Mr. Biden is the classic Senate orator, with knowledge of history and the nuances of policy and a respect for the rules of the game. He draws on the tragedies of his life — the loss of his wife and daughter in a car accident, the death of his son from brain cancer — and tales about growing up around Scranton, Pa., to relate to his audiences. He is quick with a smile that can defuse an attack.

Mr. Trump’s debating style helped carry him to victory and can still be glimpsed almost every time he appears at a White House news conference or a rally.

But Mr. Biden’s performances have been inconsistent over the course of two vice-presidential debates and through this season of nearly a dozen Democratic primary debates. Even his supporters say that, at 77, his voice is less firm and that he appears less energetic and passionate than just eight years ago. Mr. Trump has highlighted some of those moments to try to raise doubts about his opponent’s mental acuity.

The big question is which version of Mr. Biden will be on the stage Tuesday night. Typically, the first debate carries the most weight, and that might be particularly the case in a year in which so many people are casting early votes by mail and in person.

Will it be the vigorous, engaged former senator and vice president who has a firm grasp over both his own record and that of his opponent, adept at delivering the punch and nimble enough to adjust to this entirely unconventional opponent? Or will it be the Mr. Biden who sometimes seemed distracted during the early Democratic debates, sparking to life at some times but at others adrift in the tumult of a crowded stage?

A defining image from the Democratic debates was the summer 2019 exchange in which Kamala Harris, who is now Mr. Biden’s running mate, attacked him for opposing school busing earlier in his Senate career. Mr. Biden looked flustered and confused, finally saying: “I agree that everybody wants … Anyway, my time is up. I’m sorry.”

Moments after the start of the first 2016 general election debate, Mr. Trump’s strategy was clear. Again and again — amid head-spinning diversions, theatrical asides, breathtakingly brutal attacks, outright fabrications and displays of showmanship — he returned to the themes that had defined his candidacy.

Mrs. Clinton was, by his repeated telling, a tired soldier of Washington’s old guard, which had brought the nation job-killing trade deals, a dangerous nuclear arms deal with Iran, out-of-control immigration and Obamacare. (“Obamacare is a disaster,” he said at their second debate. “You know it. We know it.”)

As unorthodox a politician as he was, Mr. Trump was executing a traditional debate strategy. But over the course of those three debates, he would go places presidential candidates rarely went, showing no hesitation about launching any attack.

“Trump approaches debates not as an airing of ideas and policies, but as a reality TV show,” said Jim Margolis, who was a senior consultant to Mrs. Clinton. “Be the center of attention, say outrageous things that take time off the clock and use easily digestible catchphrases that will get repeated on the news the next day.”

When Mrs. Clinton said she was glad that “someone with the temperament of Donald Trump is not in charge of the law in our country,” Mr. Trump cut her off. “Because you’d be in jail,” he said, drawing gasps and applause from the audience.

When Mr. Trump was asked about a just-released audiotape in which he boasted in vulgar terms of pushing himself on women, he apologized and described it as “locker room talk,” adding, without a hint of a segue, “I will knock the hell out of ISIS.”

When pressed again, he attacked Bill Clinton over allegations of the former president’s sexual assaults on women, and Mrs. Clinton for standing by her husband. “There’s never been anybody in the history of politics in this nation that’s been so abusive to women,” he said.

Philippe Reines, a long time aide to Mrs. Clinton, who played Mr. Trump in her 2016 practice debates, found a formula to Mr. Trump’s approach to a debate.

“He would say I’m great, you suck, and here’s what I’m going to do,” Mr. Reines said.

“What really stuck out was how different Trump was,” Mr. Reines said. “Everyone onstage had that very stilted, thoughtful voice, sounding programmed and structured. I could see why people thought it was genuine.”

Against Mrs. Clinton, Mr. Trump was fast, intense and darkly entertaining, never yielding a second of time. He talked over the moderator and he talked over the clock as he complained he was being held to a different standard than Mrs. Clinton.

“You know what’s funny?” he said to Martha Raddatz of ABC News as she sought to get Mr. Trump to abide by time constraints. “She went over a minute over, and you don’t stop her. When I go one second over, it’s like a big deal.”

He was the opposite of the candidate measuring every word or wary of a misstep. He would throw out assertions that were false or at least or in dispute. “I did not support the war in Iraq,” he said at one point, ignoring Mrs. Clinton’s protests that he had.

On debating points, Mr. Trump might well have lost, but he was always the performer. At one debate, he paced back and forth behind Mrs. Clinton as she spoke, a shadowy figure in the background of every camera shot. Jaw out, he radiated energy, defiance and contempt for his opponent

“Please allow her to respond: She didn’t talk while you talked,” Anderson Cooper said to Mr. Trump at one point.

Sarah Palin posed a daunting challenge to Mr. Biden. He could not come across as condescending or patronizing against the Alaska governor, a woman who was new to the national stage. But he needed to show that she was not qualified to be vice president while using her as a vehicle to attack Senator John McCain, the 2008 Republican nominee facing Mr. Obama.

Dan Senor, who managed debate preparation for Mr. Ryan, studied that debate and was impressed by what he saw. Mr. Biden was unfailingly respectful. Every time she assailed him, he pivoted into an attack on Mr. McCain. He lit up with a warm smile when she said that he had been in Washington for too long.

But he was a much different opponent when it came time to face Mr. Ryan: aggressive and attacking from start to finish.

“Historically my view of Biden as a debater — I’m not sure he has all the same moves he once did — his greatest strength is he has range,” Mr. Senor said. “The notion that he’s undisciplined — you’ve not really seen that in debates.”

And even as he poked and jostled his opponent, he consistently displayed an affable manner — Mr. Biden used the phrase “my friend” 16 times in that debate. He flashed a smile to soften his words, slough off Mr. Ryan’s attacks and unnerve his opponent. “The velvet shiv,” said David Plouffe, who was Mr. Obama’s campaign manager in 2008.

Lis Smith, who was a senior adviser to the presidential campaign of Pete Buttigieg, said that every time a Democrat had tried to attack Mr. Biden during the primary debates, it backfired.

“He just laughed it off and didn’t engage,” Ms. Smith said. “It’s a disarming quality, and it’s going to be an important quality against Donald Trump, who tends to come across angry, hyperkinetic and sometimes dour on the debate stage, while Biden comes across as sunny and optimistic.”

But Republican and Democratic strategists who have studied Mr. Biden’s debate style have found that he is prone to anger if provoked, which could make him lose his train of thought or come across as haughty. “We had a ton of tape on his debating style,” said Mark Wallace, a senior adviser to Ms. Palin. “You could get under his skin.”

“He gets very preachy: ‘I know better than you,’” Mr. Wallace said. “Clearly the thing that the Trump voter and undecided voters doesn’t like is the elite who is going to preach to them.”

In the most recent primary debates, Mr. Biden showed vulnerabilities that suggested fertile ground for Mr. Trump. He struggled when pressed about his support for trade deals, the war in Iraq and a punitive criminal justice bill he championed in the Senate.

And he sometimes seemed overwhelmed by the cacophony of noise and the tumult as candidates called out to speak and moderators called for order.

But in the final Democratic primary debate, there were only two people left: Mr. Biden and Senator Bernie Sanders of Vermont. And with just one person to focus on, it seemed as if the Mr. Biden of 2008 and 2012 was back on the stage.

“Even though some critics say he doesn’t have all the moves he once had, I still thought at the end of the day, at the end of the primary season, he did pretty well,” Mr. Senor said. “And that should be worrisome to the Trump campaign.”

President Trump, accompanied by his personal lawyer, Rudolph W. Giuliani, held a news conference at the White House minutes after The Times published a major new investigation into his tax returns. 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 – The Reality TV Host vs. the Velvet Shiv: Trump and Biden in Debates