Memorable moments from political debates past

It's a hallmark of the American electoral process: the presidential debate.

Millions of people tune into the time-honored tradition, which has long been considered the ultimate showcase for candidates seeking to hold the nation's top office.

"Those are the only times we see them side-by-side," said Mitchell McKinney, a professor of political communication at the University of Akron. "They provide opportunities for candidates to either help themselves or hurt themselves."

Here's a look back at some of the most memorable debate moments in U.S. political history.

Nixon's sweating

The first nationally televised debate in history featured John Kennedy and Richard Nixon. The visuals did not play in Nixon's favor, as he was seen sweating and looking pale after previously being hospitalized for an infection, while Kennedy looked young and gave a more vigorous performance.

"There's a lot of speculation that Nixon's failure to account for the way that appearance mattered led to his failure in the debate and hence the election," said Jacob Thompson, a communications professor at the University of Nevada.

Ford's "Soviet domination" blunder

Incumbent President Gerald Ford made a critical mistake during his general election debate against Democrat Jimmy Carter.

Ford asserted there was "no Soviet domination of Eastern Europe" under his leadership, a remark that prompted the moderator to ask, "I'm sorry, what?" Ford doubled down on his answer during the debate, though later said what he meant was that the spirit of Eastern Europeans under communist control were not crushed.

"He didn't mean exactly what he said, but the damage was done," said Brandon Rottinghaus, a political scientist at the University of Houston.

Reagan shuts down age questions

Ronald Reagan, the oldest sitting president at the time, shut down some questions about his age during his debate with Democrat Walter Mondale.

"I want you to know I will not make age an issue of this campaign. I am not going to exploit for political purposes my opponent's youth and inexperience," Reagan said, prompting laughter from the room and even from Mondale.

"Mondale said in his biography later and in a documentary that you could see him on stage at that point laughing, but what was really happening in his own head was that he was crying because he knew that he had lost the debate and probably lost the election," Thompson said.

'You're no Jack Kennedy'

In this vice presidential debate, Lloyd Bentsen tore into Dan Quayle after Quayle invoked Kennedy. At the time, Quayle was drawing comparisons to the late president given both were young when assuming office.

"I served with Jack Kennedy," Bentsen said. "I knew Jack Kennedy. Jack Kennedy was a friend of mine. Senator, you're no Jack Kennedy."

Dukakis' stoicism

Democrat Mike Dukakis was widely panned for what critics said was a steely response to a 1988 debate question about the death penalty.

CNN's Bernard Shaw invoked a graphic hypothetical involving Dukakis' wife -- but the governor didn't miss a beat in his matter-of-fact response.

"Governor, if Kitty Dukakis were raped and murdered, would you favor an irrevocable death penalty for the killer?" Shaw asked.

"No, I don't, Bernard, and I think you know that I've opposed the death penalty during all of my life," Dukakis responded.

Watch glances, sighs

President George H.W. Bush was criticized for looking down at his watch during the 1992 trilateral debate with Democrat Bill Clinton and independent candidate Ross Perot.

Bush was seen glancing at his wrist after a question posed by an audience member about how the national debt personally impacted every candidate.

In 2000, Democrat Al Gore was mocked for his audible sighs during his debate with George W. Bush, as well as his decision to walk over and stand in front of Bush at one point in the debate.

Rick Perry's "oops"

In a 2012 Republican primary debate, then-Texas Gov. Rick Perry forgot part of the answer to a question about his plan to eliminate three federal agencies.

Perry named two agencies but couldn't remember the third, saying "oops."

Rottinghaus, who is currently working on a book on Perry, said the moment "was effectively the death knell of the Perry campaign, which had been languishing at that point but then was officially dead."

Christie vs. Rubio

In a 2016 Republican primary debate, Florida Sen. Marco Rubio was attacked by then-New Jersey Gov. Chris Christie for using a similar line over and over again throughout the debate.

Rubio repeatedly said then-President Barack Obama "knows exactly what he's doing."

"There it is. There it is. The memorized 25-second speech. There it is, everybody," Christie said at one point.

Christie, who ran for president again in 2024 but dropped out before the first primary votes were cast, has said the moment took down Rubio's campaign -- which Rubio has significantly pushed back on.

2020 Democratic primary debates

McKinney said two moments from the most recent Democratic primary debates stand out, the first being when Sen. Elizabeth Warren took on Michael Bloomberg.

"I'd like to talk about who we're running against: a billionaire who calls women 'fat broads' and 'horse-faced lesbians,'" Warren said. "And no, I'm not talking about Donald Trump."

Warren said she didn't believe the Democratic Party should "substitute one arrogant billionaire for another."

Another highlight, McKinney said, was Kamala Harris' challenge to Joe Biden on the issue of segregation and busing. Harris challenged Biden on his past working relationship with two segregationist lawmakers.

"There was a little girl in California who was part of the second class to integrate her public schools, and she was bused to school every day, and that little girl was me," Harris said. "I will tell you that on this subject, it cannot be an intellectual debate among Democrats. We have to take it seriously. We have to act swiftly."

Biden-Trump general election debate

President Joe Biden and former President Donald Trump's debate ultimately changed the course of the 2024 election, after a poor performance by Biden exacerbated Democratic and voter concerns about his age and fitness to serve another four years.

Pressure after the debate for Biden to step down from the ballot intensified for weeks. He announced he was dropping out of the race 24 days later.

The showdown was held in June, making it the earliest general election presidential debate ever.

Biden's raspy voice, which he attributed to a cold, coupled with his inability to hit Trump on key Democratic issues stood out from the debate as Trump steered clear of some of his more bombastic claims.

Do debates change election outcomes?

Whether debate moments are game-changers in election outcomes has itself been, well, long-debated.

Experts said scholarship shows debates typically don't shift the outcome enough to make a big difference in terms of which candidate ultimately wins or loses the race.

"At best debates provide a nudge, like in close elections in 1960 and in 2000," Rottinghaus said. "All of those moments were very punctuated and had close elections and ultimately, the debates had a slightly larger role than traditionally they would have."

The outsized effect the debate played in Biden's campaign is something of an outlier, experts said.

"There are these moments where debates really do matter and can change the course of a race, but it rarely happens," said Rottinghaus.

Thompson said there are two strong indications in social scientific data about presidential debates, the first being that voters learn from them and the second being that the educational and preference effects of primary debates are much higher than those of general election debates.

"The primary primary debates do have a big impact because people are less settled in their opinion on candidates and at the same time partisanship is playing less of a role," Thompson said.

Thompson also noted that primary debates are consequential in that they tend to have a "winnowing effect" on the field of presidential hopefuls.

"People will leave the race because of poor performance, or that poor performance leading to a reduction in their polling averages and donations to the campaign," he said.

Memorable moments from political debates past originally appeared on abcnews.go.com