WASHINGTON - Fifty-two years ago, during the first televised U.S. presidential debate, an ailing Richard Nixon perspired so profusely that it was thought to have played a role in his defeat to John F. Kennedy.
Ever since then, presidential debates have been must-see TV in America, earning their way into political folklore thanks to a legendary zinger, a spectacular gaffe or just an all-round abysmal showing.
U.S. President Barack Obama and Mitt Romney, his Republican rival for the White House, will likely create a bit of their own drama — and history — on Wednesday night in Denver, when they go head to head in the first of three debates leading up to the Nov. 6 election.
Conventional political wisdom suggests that hotly anticipated debates can often change the course of an election campaign. The American public, after all, is finally seeing the candidates in a spontaneous pressure cooker, without the handlers, the teleprompters and the like-minded audiences cheering their every word.
Nixon was apparently so mindful of his 1960 meltdown that he refused to participate in a debate against Hubert Humphrey in 1968; he ended up winning the election by a razor-thin margin. In '72, he wouldn't debate George McGovern; Nixon trounced the Democrat anyway.
Lyndon Johnson, well aware of his oratorical shortcomings, also opted against a debate in 1964, and went on to crush Barry Goldwater.
In the nine sets of presidential debates that have been held since 1960, polling giant Gallup has found that only a handful of them actually had a significant impact heading into election day.
The pollster pored over its results for the last half-century, and determined that only twice did the candidate trailing the frontrunner surge from behind post-debate to win the election — JFK in 1960, and George W. Bush in 2000. Those elections were the closest votes in almost 60 years of American presidential politics.
"The debates were less likely to be catalyst events in years when one candidate was a strong front-runner," wrote a Gallup analyst on the pollster's website.
That's not great news for Romney, who's hoping to turn around his struggling campaign with just five weeks until election day.
Obama has recently edged past him in most public opinion polls, particularly in key swing states. Some of Romney's biggest donors are reportedly pulling away, opting to invest their money in congressional candidates instead.
But one debate expert believes even if the verbal sparring matches don't dramatically swing polls, they're significant nonetheless.
"It's true that voters often watch them with their minds made up and tend to hear what they want to hear," said Allan Louden, a politics professor at Wake Forest University in Winston-Salem, N.C.
"But they change elections anyway, because they tend to define the ongoing narratives. We have a notion that Romney is out of touch and the debate may affirm to us that he is; we hear that Obama is professorial and aloof, and we may see that indeed he is. Debates are terribly important because of their confirmation or denial of the growing narrative."
The media climate is also far different in 2012 than it was even four years ago, thanks in part to the explosion of Twitter among journalists and commentators. A gaffe can quickly take on a life of its own on the social media platform, becoming fodder for 140-character ridicule that endures for days or weeks.
Two cases in point are Clint Eastwood's recent chat with an empty chair at the Republican National Convention, and Texas Gov. Rick Perry's infamous "oops" moment during a primary season showdown.
Perry never recovered from his inability to remember the three federal government agencies he was proposing to cut if elected president.
"There was a time period when campaigns had a spin room and could influence the conversation about a debate — that doesn't work anymore," Louden said.
Even way back in 2000, he noted, it was a political blogger who kept hammering away at Al Gore's exaggerated sighs in a debate with George W. Bush. The story caught on, had staying power and contributed to negative perceptions that the Democratic nominee was condescending and petulant.
"The polls may not move much but the storyline can be set and cast in stone following debates," Louden said.
They also create lasting memories.
In 1992, George H. W. Bush's glance at his watch when asked by an audience member how he'd been personally affected by the economic recession didn't do his presidential campaign any favours. It exposed a contrast between the incumbent and Bill Clinton, a folksy politician who answered with far more empathy.
Four years earlier, Democrat Michael Dukakis's clinical answer to whether he'd support the death penalty if his wife was raped and murdered was thought to have sealed the fate for his already floundering campaign.
And in 1984, Ronald Reagan deftly used humour to quell concerns about his advancing years by saying he wouldn't exploit rival Walter Mondale's "youth and inexperience." The audience roared with laughter.
Four years ago, one of the most memorable debate moments came when John McCain referred simply to Obama as "that one" mid-showdown. Pundits debated what he was getting at — was it simply condescension, or something more sinister?
In 2012, will Romney sweat like Nixon? Will Obama pull a Gore, sighing impatiently at every Romney utterance?
Obama's debate prep team has been working hard to get their man to deliver short, pithy answers and to avoid bristling with impatience at either the debate moderator or Romney.
Those guiding Romney, meantime, are working to ensure he stays calm, cool and presidential, mindful of the occasional flashes of anger he displayed during primary season showdowns and his infamous offer to bet Perry $10,000 as they sparred about public health care.
Will their efforts matter?
John Sides, a political scientist at George Washington University, recently summarized research into how debates lack clout for the Washington Monthly.
"What history can tell us is that presidential debates, while part of how the game is played, are rarely what decide the game itself," he wrote.