John McCain noses ahead of Barack Obama ?

John McCain has surged ahead of Barack Obama in opinion polls after a powerful boost from the Republican convention and his surprise choice of Sarah Palin, the governor of Alaska, as vice-presidential running mate.

Pollsters, however are divided over whether this is a decisive shift in the White House race or just a temporary boost provided by last week's successful Republican convention.

A USA Today/Gallup conducted on Friday, the last day of the convention, and over the weekend gave Mr McCain, who until very recently had been trailing narrowly in all polls, a staggering 10-point lead among likely voters.

Gallup's daily tracking poll put the Republican up by three, Rasmussen tracking had him up one while three other polls recorded a tie. Tracking polls, which take a new sample of voters each day and compile a picture of the three most recent days, are notoriously volatile.

"The burden is on Obama right now to show if he can be a credible agent for change," said John Zogby, whose Zogby International poll on Saturday gave Mr McCain a three-point advantage. "At this point, it looks as if Obama's more on the ropes than McCain."

But Mr Zogby cautioned that the McCain lead might turn out to be based on the enthusiasm generated by last week's Republican convention and therefore temporary. Most of the Monday polls reflected samples taken on Friday, the best possible day for Mr McCain because of televised coverage of his Thursday night speech, which was watched by nearly 40 million people.