It was a moment that seemed like it might change US presidential history. In his first 1976 debate with Democratic challenger Jimmy Carter, incumbent Gerald Ford gave a polished performance that saw him surge in the polls.
It was a lead that did not last long. A few weeks later, at a subsequent debate, Ford falsely asserted “there [was] no Soviet domination of eastern Europe” and declared that he did not believe Poles felt they were dominated by the Soviets.
Mr Carter went on to win the election, as the polls had predicted.
Yet while debate one-liners, exchanges, and candidate performances have produced some of the most memorable moments in US politics, few debate bon mots or gaffes have succeeded in making or breaking a candidate’s campaign — even if popular wisdom suggests otherwise, says Larry Sabato, head of the University of Virginia’s Center for Politics.
“There are debate effects, but they [fade] pretty quickly,” says Mr Sabato, who has watched every presidential debate since John F Kennedy took on Richard Nixon in the first-ever televised event in 1960. “Every four years, the debates seem very important. Whether they are or not is open to, ahem, debate.”
It is a question that both Mrs Clinton’s and Mr Trump’s advisers have been asking themselves in the days leading up to Monday night’s debate.
Take, for instance, the first debate of four between Kennedy and Nixon. Prevailing belief has held that it allowed the charismatic and cinematic Kennedy to gain an edge on the drab, dour-faced Nixon. Polls taken before the debate was aired showed Kennedy with a small single-digit lead, but his eventual election victory was by a relatively small margin — a reminder that Nixon’s countenance may have had less of an effect than people think.
Mr Carter’s 1980 debate with challenger Ronald Reagan — the only presidential debate that year — is remembered for some of Reagan’s most memorable lines, such as when he rhetorically asked the audience if they were better off than they had been four years before.
Reagan’s other famous one-liner from the debate was, “There you go again”, which he said in response to Mr Carter’s accusation that Reagan wanted to eliminate Medicare. After that, “There you go again” became Reagan’s signature rejoinder to his critics. He used it again in the 1984 debate against Walter Mondale.
Reagan already led in the polls before the debate took place.
There have been notable stumbles by sitting US presidents fighting to hold on to the White House. In 1992 George H W Bush appeared bored while checking his watch during a debate with Bill Clinton and Ross Perot. Barack Obama, meanwhile, was criticised for appearing uninterested and apathetic during his 2012 debate with Mitt Romney. The poor performance was enough to reverse the polls — Mr Obama went into the first debate with a four percentage point lead, but one week after the event he appeared on the verge of losing to Mr Romney who was suddenly ahead.
Mr Obama eventually defeated Mr Romney, while George H W Bush was a one-term president.
Yet the lessons of both men are striking. When up against contenders whom they believed were beneath them — be it a young governor from Arkansas, or a country club Republican — they let it show, a reminder that even the most polished politicians have their blind spots.
And as for any gaffes that Mrs Clinton or Mr Trump might make, the good news is that both candidates have plenty of time to recover. “There is a reason the last debate is October 19 and the election is November 8,” notes Mr Sabato.