Six decades on from John F. Kennedy’s debates with Richard Nixon, the down-to-the-wire TV encounters between presidential candidates have become a core element of the US election.
Not all of them have thrown up standout moments; original Kennedy-Nixon duel has stuck in the collective memory not because of a single line, but because the Republican candidate spent much of it flustered and visibly sweating next to his cool younger rival.
But over the elections since, there’s been a steady supply of bizarre, hilarious and occasionally disturbing incidents caught on camera for posterity. With too many to count, here’s a mere selection.
Age before beauty
Back in 1980, Ronald Reagan fought two debates against floundering incumbent Jimmy Carter. He had a particularly good time of it in the second, delivering his classic “there you go again” line and a stirring closing monologue in which he asked the audience whether they were better off than they were four years ago. (As Mr Carter found out that November, their verdict was no.)
Four years later, when fighting for re-election, the elderly president stumbled badly in his first debate with Walter Mondale, appearing confused about basic facts and tripping over words. Asked about it at the next debate, he flipped the script: “I will not make age an issue of this campaign,” he smiled. “I am not going to exploit, for political purposes, my opponent's youth and inexperience."
Twelve years later, the age question would be reversed to a Democrat’s advantage, when Bill Clinton was asked about 73-year-old Bob Dole. "I don't think Senator Dole is too old to be president,” Mr Cinton remarked. “It's the age of his ideas that I question."
The all-time greatest
Possibly the all-time greatest debate comeback belongs to 1988 vice presidential candidate Lloyd Bentsen, who slapped down George H. W. Bush’s notoriously inept running mate Dan Quayle for comparing himself to John F. Kennedy in an answer about experience.
“Senator,” Mr Bentsen intoned, “I served with Jack Kennedy. I knew Jack Kennedy. Jack Kennedy was a friend of mine. Senator, you're no Jack Kennedy."
“That was uncalled for,” said Mr Quayle. Nobody agreed.
Bush v Gore
The 2000 election is mainly remembered for the Kafkaesque mess in Florida after polling day, but before that came a string of bizarre debate performances that badly damaged Democrat Al Gore.
In his first face-off with George W. Bush, he ostentatiously sighed and pulled contemptuous faces while his rival was speaking. And in their now-traditional town hall-style roving microphone session, Mr Gore made the strange decision to stride up to Mr Bush while he was speaking and loom over him like an obelisk. Mr Bush simply paused mid-flow, looked at his rival and gave a cheeky nod.
Sometimes even a throwaway of lines can take on a life of its own. So it was with Mitt Romney’s 2012 boast about trying to hire more women when he was governor of Massachusetts.
“We took a concerted effort to go out and find women who had backgrounds that could be qualified to become members of our cabinet,” he recalled. “I went to a number of women's groups and said, 'Can you help us find folks?' and they brought us whole binders full of women."
The tin-eared phrase “binders full of women” had become a meme even before the debate had finished, and it survives as a shorthand for disingenuous diversity-signalling to this day.
The trials of Hillary Clinton
The former first lady, senator and secretary of state was a presidential debate veteran by the time Donald Trump defeated her: three debates against him, nine against Bernie Sanders and the other 2016 Democratic candidates, and more than 20 in the marathon 2008 contest.
During that year’s New Hampshire debate, she was asked by a moderator to account for why voters found her less “likeable” than Barack Obama. “Well, that hurts my feelings,” she replied, to applause. “But I’ll try to go on ... I don’t think I’m that bad.”
“You’re likeable enough, Hillary,” said Mr Obama with a dismissive glance.
A few days later, she trounced him in a primary that had been expected to knock her out of the race.
In 2016, though, she faced character assassination of a completely different calibre. The second of her two debates with Mr Trump saw her rival stalk her ominously around the room – and worse. “It's just awfully good that someone with the temperament of Donald Trump is not in charge of the law in our country,” she said during a discussion on fact-checking and falsehoods.
“Because you’d be in jail,” replied Mr Trump – setting up four years of insisting that his rivals are illegally conspiring to destroy him.
With as many as 20 candidates now routinely – and sometimes inexplicably – throwing their hats in the ring each cycle, the primary debates have yielded all manner of off-the-handle incidents.
In 2012, Rick Perry forgot his own signature campaign promise to abolish three government departments (“What was the third one there? … Oops.”); in 2016, Marco Rubio inexplicably repeated the same answer four times even as Chris Christie accused him of being a robot, while another debate that year descended into a barely-euphemised row over penis size.
But for some candidates, 2020 was even tougher. In February, Elizabeth Warren delivered one of the most devastating blows ever unleashed by one candidate upon another: a full-minute monologue dismantling Michael Bloomberg.
“Look, I'll support whoever the Democratic nominee is,” she said. “But understand this: Democrats take a huge risk if we just substitute one arrogant billionaire for another.” She lost the nomination, but won credit for helping destroy Mr Bloomberg’s campaign almost before it began.