THE pressure is on Barack Obama to crush John McCain, his Republican rival, in the first face-to-face presidential debate at the University of Mississippi on Friday.

The Democrat regained his lead in the polls over McCain as the economy tottered last week. It was a potentially pivotal burst of momentum. But Obama’s performance in the debate could determine whether it marked the start of a decisive shift towards him – or just another blip in the final weeks of a closely fought election.

Obama, 47, has yet to convince voters that he is ready for the White House. If the polls show the two candidates still neck and neck in the run-up to November 4, most pundits believe that McCain will have the advantage as the more familiar politician with the military experience to become commander-in-chief.

The three presidential debates and one vice-presiden-tial showdown will take place in just 2½ weeks. “Debates freeze the election,” said Larry Sabato, director of the University of Virginia’s centre for politics. “Nothing happens while they are held. Tens of millions of people watch them. Partisans tune in to cheer their side, but it is the moment when independents make up their minds.”

Obama has recovered his support among white women after they deserted him for Sarah Palin, according to a CBS poll last week which showed that he had turned a 19-point deficit into a two-point lead in just nine days.

He now has to turn on the wit and charm and make good use of his youth to draw a contrast with the veteran McCain, 72, reinforcing his message of change. However, McCain, who has a stiff, cheesy delivery style for set speeches, can be quick on his feet.

Todd Harris, a Republican consultant and former McCain adviser, said: “Expectations will be quite high for Obama because of his rhetorical abilities, but the fact is he’s not that great a debater. When he’s not giving Teleprompter speeches he comes across as quite professorial and far too analytical. McCain has a great sense of humour. Every candidate enters a debate with canned one-liners but he can actually make jokes on the fly.”

Obama’s performance in debate against Hillary Clinton during the primary season disappointed many of his supporters. His patronising comment, “You’re likable enough, Hillary”, is thought to have cost him the New Hampshire primary.

Bill Clinton sounded a sceptical note about Obama’s abilities this weekend when he suggested that the race could remain tied until the election, “barring some unforeseen development” in the debates.

The debates have helped to pick winners ever since a youthful John F Kennedy squared off against a sweating Richard Nixon in the 1960 election. The camera lights were to blame but Nixon looked nervous and shifty. Jimmy Carter went on to defeat Gerald Ford in 1976 after the sitting president confirmed his reputation as a bum-bler by saying: “There is no Sovi-et dominance over eastern Europe.” Al Gore’s sighs of impatience at George W Bush’s answers in 2000 reminded voters why they disliked eggheads.

McCain challenged Obama to a series of town hall meetings over the summer in the hope of blunting his poll lead, but Obama declined to engage in any unnecessarily risky face-offs. “It was a mistake to refuse,” Harris said. “If he had bested McCain, it would have been a big momentum-builder for Obama over the summer.”

In the nearest thing to a head-to-head encounter, McCain and Obama were questioned by Rick Warren, author of The Purpose-Driven Life, at his California megachurch last month. Few people watched as it was at the height of the Olympics, but McCain was widely considered to have won.

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