After weeks of flinging mud at each other on the campaign trail, Barack Obama and John McCain are preparing for what could turn into a seminal moment in the election, a bout of single combat in the form of a televised debate watched by a huge national audience.
With the race for the White House neck and neck and the financial markets in turmoil, interest in the debate, being held in Oxford, Mississippi, is expected to be unprecedented.
The stakes are especially high for Senator Obama, whose prickliness and long-windedness make him an easy target for his rival. John McCain has a well-deserved reputation for slamming his opponents while tap-dancing his way out of tricky situations. The former fighter pilot relishes the give and take of single combat.
One of Mr McCain's favourite tactics in debate is simply sitting grinning to the cameras with his hands folded while his rivals say their piece. The danger that Mr Obama's advisers see is that their sometimes-humourless candidate will fall into an all-too-familiar mode of lawyer and law professor.
This week Senator Obama is holed up at a special "debate camp" in Tampa, Florida, where one of his few grey-haired advisers, a hard-nosed Washington lawyer Greg Craig, is sparring with him. Another practice opponent is Ron Klain, who was part of the team that helped John Kerry and Al Gore prepare for debates during their failed presidential bids. Kevin Spacey played him in the movie Recount, about the 2000 Florida "hanging chad" debacle.
Senator McCain's campaign is not saying who he will use for sparring practice but he is being advised by Brett O'Donnell, a champion debating coach from the televangelist Jerry Farwell's Liberty University. The campaign angrily repudiated an earlier report that it was using a prominent black Republican, Michael Steele, to play Mr Obama in practice debates. The first debate takes place at Ole Miss, as the University of Mississippi in Oxford calls itself, and it will focus on foreign policy, widely acknowledged to be Mr McCain's strongest suit.
Mr Obama dislikes the informality of televised exchanges and considers the rapier-like quips and soundbites to be a distraction from the important task of healing America's multiple problems. Many voters are only tuning into the election at this late stage, however, and the history of presidential election debates shows that a candidate's likeability is often more important than his experience or stance on the issues.
Mr McCain has the instincts of a blade-carrying street fighter and is capable of trapping his adversary and plunging a rhetorical knife between his ribs. That is how he emasculated Mitt Romney in a Republican primary debate this year.
"Well, Governor," he exclaimed in a voice dripping with condescension, "I'm astounded that you haven't found out what waterboarding is," turning the debate towards his own experiences at the hands of his North Vietnamese jailers when he was a prisoner of war. Mr McCain's contempt for an adversary whom he does not believe has paid his dues is scarcely disguised and he is expected to poke and provoke him to expose his weaknesses.
The Obama campaign is deeply wary of the coming encounter. "Despite the fact that we got the chance to do this a lot during the primaries, these debates are not by any stretch of the imagination his strong suit," said Robert Gibbs, a senior strategist. "He likes to talk about a problem, give some examples that address some solutions and oftentimes that doesn't fit into the moderator's allotted time."
That may be exactly what the McCain camp is hoping for. Some of Mr Obama's worst moments in the campaign have come during the debates and forums where his earnest long-windedness has got the better of him. Over the gruelling months on the campaign trail he has hardly improved from one of his worst moments during a debate with other Democrats when they were asked how they would deal with terrorists. "Let's do everything we can to destroy them," responded Hillary Clinton.
When his turn came Senator Obama rambled on about engaging the international community and he had to ask for a second chance to reply.
Make or break? The great TV debates
* America's first televised debate in 1960 was a disaster for Richard Nixon, who was pitted against John F Kennedy. Nixon had the flu and was hobbling from a leg injury. His sweaty image did more to destroy him than anything else. He looked so bad that his mother called up to check on him.
* In 1980, President Jimmy Carter was up against Ronald Reagan. He irritated viewers when he responded wearily to criticism, saying: "There you go again." Reagan scored highly by asking the simple question: "Are you better off than four years ago?"
* In 2000, Al Gore showed his aggravation with the misleading answers given by George W Bush and the voters punished him for it. Their first debate is remembered as the one Gore won on the night and then lost in the spin that came afterwards.Reuse content