Presidential debates have always been political theater. Here are some of their most memorable moments.

The debate between John F. Kennedy and Richard Nixon in 1960 was the first ever televised presidential debate. 

Discussions on this debate have often focused on the fact Kennedy wore makeup during the debate but Nixon refused. Historians debate the extent to which this hurt Nixon, but the narrative surrounding this debate has been that Kennedy looked youthful and strong while Nixon looked gaunt and pale. 

Julian Zelizer, a professor of history and public affairs at Princeton University, told Time in 2019 this set "the standard and creates the idea that debates are not simply about the substance, but also the presentation."

Kennedy's performance in the first debate changed the history of presidential elections and candidates began to recognize the power of television and importance of appearance.

Some candidates became so wary of how TV could impact an election that after the 1960 campaign season the next televised debate did not occur for another 16 years. Former President Lyndon B. Johnson, for example, refused to debate in 1964 — as did Nixon in 1968 and 1972.

"THE BLOOPER HEARD ROUND THE WORLD."

That was Time's headline after President Gerald Ford in a 1976 debate versus Jimmy Carter declared there was "no Soviet domination of Eastern Europe."

"There is no Soviet domination of Eastern Europe and there never be will under a Ford administration. ... I don't believe the Poles consider themselves dominated by the Soviet Union," Ford said.

It was the height of the Cold War and the Soviet Union had a strong grip over the entire region at the time, making Ford's remarks at odds with reality. 

The moderator at the time, Max Frankel of The New York Times, responded, "I'm sorry, what?"

The line would haunt Ford through the rest of the campaign season, and he eventually lost to Carter. 

Ronald Reagan, a former actor, was a natural during presidential debates and had a knack for winning over the crowd with one-liners. He showed off this skill in a 1980 debate with Jimmy Carter. 

After Carter delivered a lengthy and intricate monologue on healthcare, Reagan looked at him with a smile and said, "There you go again." 

Reporting on the debate at the time portrayed Carter as lacking a sense of humor and far too serious while Reagan was viewed as "calm and reasonable," the Economist reported.

Reagan showed that delivering a quick zinger in a debate could quickly shift the conversation away from policy and devastate an opponent. 

The former California governor went on to defeat Carter, making him a one-term president.

Reagan showed off his skills as a performer once again in a 1984 debate with Minnesota Democrat Walter Mondale. 

After a poor performance in the first televised debate against Mondale, some began to raise concerns that Reagan's age was becoming a problem. Reagan was 76 at the time, and some felt he was too old to serve a second term as president. 

Reagan was able to alleviate concerns about this with his sense of humor. 

When the moderator asked Reagan about whether his age could be an issue, he replied, "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."

The audience, and even Mondale, exploded with laughter. Reagan used charm to his advantage once again, and he went on to win the election.

The 1988 vice presidential debate between George H.W. Bush's running-mate, Dan Quayle, and Michael Dukakis' running-mate, Lloyd Bentsen, did not change the course of the election, but it did deliver one of the most memorable one-liners in presidential debate history. 

Quayle, a Republican senator from Indiana, tried to compare himself to former President John F. Kennedy in the debate. He was young and trying to dismiss concerns about lacking experience.

Bentsen, a Democrat from Texas, was not having it. 

"I served with Jack Kennedy. I knew Jack Kennedy. Jack Kennedy was a friend of mine. Senator, you're no Jack Kennedy," Bentsen said, prompting a roar of applause from the crowd.

Sometimes it's not what candidates say but their general demeanor that determines how their performances in a debate are graded and remembered. 

In a 1992 town hall-style debate with Bill Clinton, an audience member asked Bush about national debt. 

As the audience member began to ask the question, Bush took a quick look at his watch. Bush, who was president at the time, came off as though he didn't care about or have time to listen to the concerns of regular Americans. 

He went on to lose the election to Clinton, and was a one-term president.

During a 2000 town hall-style debate between then-Texas Gov. George W. Bush and then-Vice President Al Gore, the younger Bush showed that you don't need to use words to make people laugh and win over the crowd. Sometimes just a simple gesture will do the trick. 

Gore berated Bush with condescending, wonky attacks throughout the debate. At one point, as Bush was answering a question, Gore got up and started walking toward him. 

It seemed as though Gore wanted to intimidate Bush, but it didn't work. Bush looked at him and gave him a quick nod, which prompted laughter, and then continued his answer. 

After, Gore's team thought he'd won the debate on policy but "on mannerisms and the takeaway, he ended up losing," commentator George Stephanopoulos said at the time, the Atlantic reported.

Bush "opened up a lead in several polls" within a week, Time reported, and would go on to win the election.

"The 1980s are now calling to ask for their foreign policy back because the Cold War's been over for 20 years."

That was Barack Obama's big zinger in a 2012 debate against Mitt Romney, as the president sought to dismiss his Republican challenger's assertion that Russia was the country's "No. 1 geopolitical foe."

It was one of the most-talked about moments after the debate, and seen as a blow to Romney (who ultimately lost the election).

But the line did not age well, as Russia annexed Crimea roughly two years later. It proved that a candidate doesn't necessarily have to be correct to be perceived as winning the argument.

After the first GOP presidential primary debate of the 2016 campaign season in August 2015, CNN reported, "It was the most dramatic opening to a presidential debate in recent memory —and Donald Trump stole the show before he'd even said a word."

Indeed, no candidate on the stage could outmatch Trump in showmanship, who used his experience as a reality TV star to his advantage.

"One of the things people love about you is you speak your mind and you don't use a politician's filter," moderator Megyn Kelly said to Trump toward the beginning of the debate. "However, that is not without its downsides, in particular, when it comes to women. You've called women you don't like fat pigs, dogs, slobs, and disgusting animals."

Trump interrupted Kelly and said, "Only Rosie O'Donnell." The crowd roared with applause and laughter. 

Trump proved that you don't have to be the most polished person on the stage to win in the end. 

"For more than a month, Trump has defied the normal patterns of politics and Thursday night was no exception," CNN reported at the time.

During the first presidential debate of the 2020 election, Trump continuously interrupted Biden as he answered questions posed by moderator Chris Wallace, leading to bickering between the candidates.

As Biden attempted to respond to Wallace's question about whether he planned to add justices to the US Supreme Court, Trump interrupted him again, repeating, "Are you going to pack the court?"

"Will you shut up, man?" Biden said. "This is so unpresidential."

Another moment that made headlines was Trump's apparent refusal to condemn white supremacist groups. When asked to tell white supremacist groups to "stand down" by Wallace, Trump instead said, "Proud Boys, stand back and stand by," referencing the far-right, neo-fascist group.

A high-ranking member of the Proud Boys told the House January 6 panel that membership in the organization "tripled" after Trump's remark, Insider's Cheryl Teh reported.

CNN's Jake Tapper called the debate "a hot mess inside a dumpster fire inside a train wreck."