As George W Bush and John Kerry limber up for their third presidential debate, BBC News Online examines historical debates that have represented turning points - both good and bad - for the candidates.
By Clare Murphy
BBC News Online
Al Gore's frontmen may have talked up their expectations of George Bush's performance prior to the 2000 presidential debates.
Nixon had not considered that there was more to it than policy
But the encounters were supposed to prove to American voters that the experienced Washington insider was a far better choice than a Texan governor seen by some as decidedly dim-witted.
Mr Gore did indeed display an admirable grasp of detail - showing up on several occasions gaps in Mr Bush's own knowledge.
To little avail, however. The pundits may have declared him the winner, but when it came to that more elusive attribute - likeability - the Texan emerged victorious.
It is the box Bill Clinton ticked in 1992 during an unscripted moment with a member of the debate audience. But it was Ronald Reagan, with his one-liners that demolished opponents' carefully constructed attacks, who most clearly established the rule that debates are not so much about the policies but the personal.
Me and you
The presidential debate offers two prospects: firstly, the opportunity to shift negative impressions of oneself, and secondly the hope that those of one's opponent will be cemented - preferably by their own doing so that one avoids appearing mean-spirited.
Supporters of John Kerry believed he did the former during the first debate - winning some new respect for his strength and trustworthiness, according to opinion polls.
But grimaces and apparent annoyance on the face of the president while his opponent was speaking did not help George W Bush.
It was reminiscent of 2000, when Al Gore's eye-rolls and exaggerated sighs at Mr Bush's blundering not only made him seem mean - an impression which had also worked against the dry-witted Republican Bob Dole in his debates with Bill Clinton in his 1996 campaign - but also provided ample ammunition to those keen to portray him as arrogant.
Mr Gore's insistence on details - such as explaining that Yugoslavia comprised both Serbia and Montenegro - was jumped on as evidence that he was not just arrogant, but also a tedious swot.
Dukakis played into Bush's hands in the 1988 debate
Twelve years earlier, Michael Dukakis had similarly obliged George Bush's father, who had sought throughout the campaign to portray the Democrat as a cold, technocratic liberal - largely based on Mr Dukakis' opposition to the death penalty.
When Mr Dukakis was asked by a journalist whether his feelings on capital punishment would change if his wife Kitty were raped and murdered, he replied with cool objectivity that they would not.
He failed miserably to supply the emotion that the American public apparently wished from a candidate when confronted with the hypothetical killing of his wife.
The clip, which was played over and over again, came to sum up his campaign. The "cold liberal" label stuck.
But hoping that one's opponents will play ball and hit home their flaws is a dangerous game.
No-one learned this to more devastating effect than Richard Nixon.
In 1960, the vice-president had hoped that appearing head-to-head with the lesser known Massachusetts senator in the first ever televised debate would bring home to voters that John F Kennedy was far too inexperienced for office.
But their respective policy differences over two small islands off the coast of China were lost in the stark contrast between a Nixon who looked so pale and unwell that his mother phoned him up afterwards to ask if he was OK, and a tanned, relaxed Kennedy.
It did not matter that those listening to the debate on the radio believed the vice-president to have emerged the clear winner - the on-screen poise of the younger, lesser-known man dispelled any notion that he was too young and inexperienced for office.
Twenty years later, Ronald Reagan would masterfully desist efforts to caricature him with a couple of simple, perfectly timed remarks.
Jimmy Carter hoped to fend off the Reagan challenge to his second term in office by portraying the Californian governor as a dangerous conservative.
"There you go again": Reagan took the wind out of Carter's attacks
But his detailed attacks on the nature of Reagan's policies were cut short with the casually delivered line - "There you go again", simultaneously writing off the president as a boring policy wonk - while establishing himself, Reagan, as genial and infinitely electable.
When Reagan met his own challenger for the presidency in 1984, he would again prove that the witty, confident remark wins more points than a clever grasp of policy.
In his first debate with Walter Mondale, he appeared positively befuddled against his opponent's mastery of detail, and post-debate polls showed some concern about whether Reagan was, at 73, too old for office.
But when Mr Mondale sought to make this an issue in the second debate - Reagan swiftly retorted: "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."
In one fell swoop the Reagan voters liked had returned: confident, witty and presidential.
But while debates can be pored over after the election results for evidence of where it all went wrong, their impact on the result is in and of itself a subject for debate.
Debates may offer some memorable moments which come to symbolise when a campaign died, but George Bush senior did not lose the election in 1992 because he looked at his watch while being questioned by voters, nor was Gerald Ford booted from the White House because he insisted - at the height of the Cold War - that Eastern Europe was not under Soviet domination.
Nonetheless debates do have the potential for upset. This may well explain why after the first such televised encounter took place in 1960, everyone steered clear for the best part of two decades.
They are now an established part of the campaign, and while not obligatory, they are no longer truly optional.
And given the opportunities for slips, solecisms, and sweating that the floor offers, it is perhaps unsurprising that the terms and conditions for the Bush/Kerry confrontations have reportedly taken weeks of private, heated negotiation - from room temperature to podium height.