As the two contenders limbered up for tonight's second US presidential debate, an opinion poll published today suggested that Senator John Kerry's strong performance in the first electoral face-off has given him a slight edge with voters.

Capping a difficult week for President Bush's re-election campaign, the Associated Press poll showed that three-quarters of "likely voters" had watched the first televised debate - and of those 39 per cent came away with a more favourable view of Mr Kerry.

Only 8 per cent said they had felt better about Mr Bush after a stumbling, uneasy performance in which Mr Kerry repeatedly attacked his handling of the conflict in Iraq.

"I was more comfortable with Kerry after the debate," Louis Robinson, a 66-year-old retiree, told the AP. "I just like the way he carried himself."

Eric Schlichting, an inventory manager who tends to vote Republican, said he was losing confidence in Mr Bush's ability to control the crisis in Iraq. "He sticks to his guns, but his aim is so far off that sticking to his guns is not paying off," he said.

Among 944 likely voters, the AP-Ipsos poll completed yesterday gave Mr Kerry 50 per cent of the vote against 46 for Mr Bush.

With a margin of error of three points either way, that is far from conclusive, but other recent polls have clearly demonstrated that Mr Bush has lost the momentum gained with the Republican Party convention in New York last month and show that Mr Kerry is making ground in key "battlefield states".

More ominously for the Bush campaign, the President has lost a 20-point lead he had a month ago on the question of who would better protect the country. His lead on that bedrock issue is now down to six points. AP said less than half, 44 percent, of likely voters approve of his handling of the war in Iraq, down from 51 percent in a similar poll three weeks ago.

Mr Bush's advisers privately acknowledge that in the first debate he harmed his case by fidgeting and grimacing during Mr Kerry's answers, and failing to seize upon openings the Democrat gave him.

But they say that Mr Bush will be sharper - and tougher on his opponent - during tonight's debate in St Louis, Missouri, in which the two men will take questions from undecided voters.

Missouri is seen as the ultimate bellwether state: only once in the past 100 years has it failed to back the eventual winner. Mr Bush carried the state with a 3.5-point lead in 2000 and has enjoyed a clear lead in recent months despite the state's economic problems - it has lost 131,000 jobs, mostly in manufacturing.

But one statewide Missouri poll since last week's first presidential debate showed Mr Kerry clawing back ground to be only two points behind the incumbent - within distance of victory if he can keep his campaign on course.

A separate poll published yesterday showed Mr Bush and Mr Kerry in an effective "dead heat race" for the White House. The Zogby/Reuters poll gave Mr Bush a 46-44 lead against Mr Kerry, with minor candidates 2.3 percent of the vote and eight per cent of voters undecided.

The pollster John Zogby said that the Kerry campaign enjoyed a clear advantage on America's east and west coasts and Mr Bush enjoyed a 20-point lead in the South.

But in the American heartland - which delivered Mr Bush victory four years ago - the two were tied at 43 per cent support each.

The poll also showed Mr Kerry enjoying a 25-point lead among those aged 18-29 while Mr Bush has a 16-point lead in the 30-49 age group. Voters over 50 are split equally.

And the "marriage gap" is huge: the Bush campaign enjoys a 13-point lead among married voters, while single voters back Mr Kerry by 57 to 30 per cent.

"Remember, this is larger than Bush versus Kerry," Mr Zogby said. "This is two equal-sized nations going to war."

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