On Thursday, President Joe Biden and former President Donald Trump will meet on stage in Atlanta for the first of two presidential debates ahead of the November 2024 election. While their performance in the televised debates could influence the outcome, it wouldn’t be the first time in history that a presidential debate moved the needle in a close race.
Presidential debates have been a staple of campaigns for decades, and history has shown that they can have the power to sway undecided voters and solidify public perception of the candidates. During debates, candidates stand beside their opponents and present their policies, personality, and vision to millions of viewers—often the biggest audiences of their campaigns. For instance, some 73 million people viewed the first Biden-Trump presidential debate in the lead-up to the 2020 election.
Patrick Stewart, a political science professor at the University of Arkansas, says that while there have been advancements in technology and changes in media consumption over time, the presidential debates still offer candidates an unparalleled opportunity to present their stances on issues and pitch themselves and their vision for the country. “As we have seen with our politics these days, flipping the margins a little bit influences elections,” he says. “And we have seen that in many of the elections.”
TIME spoke to several historians about the most important presidential debates and their impacts on the course of American history.
John F. Kennedy vs. Richard Nixon (1960)
The first debate between Kennedy and Nixon is considered one of the most significant because it entrenched the idea that appearances are an important part of presidential campaigns, says Alan Schroeder, a professor of journalism at Northeastern University. The debate is considered the first nationally televised presidential debate in history.
The best-known narrative about the debate is that Nixon, then Vice President, ultimately lost the election because he looked old and tired during the debate, while Kennedy, then a Senator from Massachusetts, wore makeup and appeared young and vibrant. People who watched the debate on television generally believed that Kennedy had won the debate, but those who listened to their speeches on the radio believed that Nixon had performed better, according to the oft-repeated analysis of the 1960 election.
However, some historians argue this explanation doesn’t hold up due to differing demographics between TV viewers and radio listeners. "It likely was the case that the debate helped Kennedy look younger and more presidential, but we have very little empirical research to suggest that’s why he won the election,” says Mitchell McKinney, a political communication scholar and dean at the University of Akron.
The debate’s biggest effect on public opinion was that it allowed Americans to see—or hear—the two candidates together. “That first debate probably made a big difference in Kennedy's favor because it legitimized him,” Schroeder says. “He was the underdog. Nixon was the sitting Vice President, and the more experienced and better known candidate nationally. But Kennedy had a very good series of performances in those debates that undoubtedly helped him.”
Jimmy Carter vs. Gerald Ford (1976)
After the Nixon-Kennedy election, a long period passed without any general election debates until President Gerald Ford fell behind during the 1976 campaign and decided he needed to debate then-Georgia Governor Jimmy Carter. McKinney says that Ford was "relatively unknown" to the public despite being the incumbent President, and not many people were familiar with Carter either. "They needed the exposure from the debates to help voters really get to know them,” he says of the matchup.
The debates are best remembered for a single moment during the pair’s second debate when Ford declared, “There is no Soviet domination of Eastern Europe, and there never will be under a Ford administration.” The moderator, Max Frankel of the New York Times, was unable to hold back his surprise: “I’m sorry, what?… Did I understand you to say, sir, that the Russians are not using Eastern Europe as their own sphere of influence in occupying most of the countries there and making sure with their troops that it’s a communist zone?”
It’s not clear whether the gaffe ultimately shifted the outcome of the election, which Carter won. But historians argue that the moment was particularly damaging for Ford because of the media reporting after the debate, which contributed to the narrative that he was clumsy and not up for the presidency. “You have to show that you can respond to the questions effectively,” Stewart says. “Someone who is able to be circumspect and has a good memory so we can get an idea as far as what they actually would do under pressure.”
Other scholars have suggested that there isn’t polling evidence that the debate hurt Ford’s campaign. “I wouldn't say that Ford lost the election because of that,” Schroeder says. “It certainly didn't help him… but it does show you certainly the power of a mistake that gets then magnified and the need to very quickly correct it.”
Jimmy Carter vs. Ronald Reagan (1980)
For most of the 1980 campaign cycle, Carter had been unwilling to debate Ronald Reagan, the former California Governor, who was considered a master of visuals and humor. But Carter changed his mind about 10 days before the election, realizing that he was trailing in the polls and needed a last minute pitch to undecided voters, McKinney says.
While Carter peppered his rhetoric with facts and policy, Reagan countered with one-line catchphrases, including “Are you better off than you were four years ago?” and “There you go again.” Reagan went on to win the election one week later, in part, because he understood a fundamental of the debates, experts argue. “Reagan came across as very confident and amiable in that debate,” McKinney says, “whereas Carter seemed to be under siege coming out of a hostage crisis, and he wasn’t able to reassure the public.”
George H.W. Bush vs. Bill Clinton vs. Ross Perot (1992)
Unlike most other presidential debates, where candidates stand at lecterns and respond to moderator questions, the second debate in 1992 was conducted in a more relaxed "town hall" format suggested by Bill Clinton’s campaign. The format was seen as benefiting Clinton, then-Governor of Arkansas, who voters thought seemed more likable than his opponents over the course of three debates.
In one famous moment during the second debate, President Bush was caught on camera looking at his watch as a voter in Richmond, Va. asked a question about the national debt, giving viewers the sense he was being passive or bored. “Every little gesture or word is subject to a lot of scrutiny,” Schroeder says, adding that it fed into the narrative that Bush was out of touch with the lives of voters.
The debates also introduced the public to third-party candidate Ross Perot, who garnered 18.9% of the vote, one of the most successful third party runs in American history. Exit polls suggested that Perot took votes from Clinton and Bush about equally, although some experts still disagree about Perot’s effect on the race. Mary Matalin, Bush’s former campaign director, later said that she was “absolutely convinced” that Perot cost Bush the election. “He got us off message. Every event that we found ourselves in—particularly the debates with him—caused President Bush to underperform,” Matalin said.
George W. Bush vs. Al Gore (2000)
In the tight 2000 election, which was ultimately decided by the Supreme Court, the debates were particularly important. Vice President Al Gore had been in high-profile debates before, whereas Texas Governor Bush was a relative newcomer known to stumble over his words.
"Going into the debates, Gore was in a better position," McKinney says, "but he was seen as more aggressive and people didn’t find his style or demeanor that comfortable."
During the first debate, microphones caught Gore loudly sighing in response to Bush’s answers, and he was seen on the screen rolling his eyes and shaking his head in frustration at other points. At the third debate, Gore walked up to Bush as he was speaking, perhaps to intimidate him. Bush smirked and continued on, prompting the audience to laugh.
As TIME wrote in 2000, “Last week, George W. Bush and Al Gore stood at podiums, and Gore, as befitting the furniture, gave what came across as a lecture: correcting his opponent, holding forth, sighing in exasperation at Bush’s answers. The pundits and the polls agreed: Gore had won the debate. Then he lost: within a week, Bush had opened up a lead in several polls, as voters apparently decided they were tired of Professor Know-It-All.”
Joe Biden vs. Donald Trump (2024)?
Historians say that presidential debates matter the most when there’s no clear frontrunner in the polls and undecided voters still make up a large chunk of the electorate. Both of those conditions could be true this year.
Polling data from FiveThirtyEight shows that Trump leads Biden by about one point nationally, and other polls show that roughly 10% of voters are still undecided. “These debates are so important because this election will likely be decided by just a percent or two,” McKinney says, comparing the current cycle to the Bush-Gore 2000 race that was so close that only several hundred votes in Florida determined the winner. “If you go back and look at the polling that year, it’s exactly the same case today.”
But that’s not the only reason the Biden-Trump debates have the potential to be significant. The debates are set to feature the two oldest major-party presidential candidates in history, and particular attention will be given to their age, stamina, and mental fitness. Trump, 78, has repeatedly called Biden, 81, too frail to handle a second term. “Television is a visual medium and people are going to be looking very closely at both of them,” Schroeder says. “One of the biggest tests is their stamina. When you’re in a debate for that long, you have to be at the top of your game. You have to be aware that the camera is on you.”
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Write to Nik Popli at nik.popli@time.com