The campaign of Barack Obama was given a fresh boost today on the eve of his second televised debate against John McCain after it emerged that the Democrat had secured a greater number of new voter registrations in crucial target states.

As the deadline for registrations arrived today, the Washington Post reported that electoral rolls had expanded by about four million voters in a dozen key states over the last year, with the Democrats clinching a significant advantage.

In particular, the ratio in favour of Mr Obama of new voters registered was reported as being as high as 6 to 1 in some key states, amid a huge effort by the Obama campaign to 'get out the vote' in swing states.

According to the Post, new voter registrations this year in Florida are more than double those of the Republicans. In North Carolina the figure is 6 to 1 and in Colorado and Nevada it is reported as being 4 to 1.

The newspaper says that 11 states targeted by the Obama camp - which were won by President Bush in 2004 - have seen a big increase in new, primarily Democratic, registrations. These are Ohio, Florida, Georgia, Virginia, Indiana, Missouri, Colorado, Iowa, Nevada, New Mexico and North Carolina, where Mr Obama is preparing for tomorrow's debate with Mr McCain.

It quoted figures showing that the Obama campaign had gained 800,000 new voters, and the Republicans had lost 200,000.

Republicans acknowledged the success of the Democrat campaign in insipring new voters to register. But senior figures say that this does not mean they will actually come out to cast their ballot on polling day.

"The machine that has been put in place by the Democrats is effective," said Brian K Krolicki, the Republican lieutenant governor of Nevada. "They have a lot of people holding clipboards." However, he told the Post: "There's a difference between successful registration and a groundswell."

News of the registrations come as a further blow to the McCain campaign with only 29 days until the election, as the Republican candidate faces an electoral map that has shifted significantly in favour of Mr Obama in the past fortnight.

With Mr McCain considered to have blundered during the recent economic crisis - and with his vice-presidential candidate Sarah Palin showing an embarrassing failure to grasp some of the key issues in interviews and a televised debate - there are fears that the wheels are coming off the Republican's campaign at the most critical time.

It has triggered a decision to try to move the attention of voters back on to questions about Mr Obama’s past associates and character, with a message that the Democrat is somehow not American or patriotic enough to be President.

Yesterday, the Republican party accused Mr Obama’s campaign of accepting illegal contributions, claiming it had taken donations that exceeded federal limits and also some from foreigners. It said that it had asked election officials to look into the matter.

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