Hurricane Sandy's landfall in the northeast, meanwhile, could potentially further play into Romney's surge, hurting Obama's drive to encourage voters to vote early and forcing him off the campaign trail to return to the White House.

No Republican has won office without Ohio; and the last Democrat to do it without Ohio was John F. Kennedy, in 1960. It is one of the four out of 11 or so battleground states that Romney needs to win to secure victory.

At the weekend, Romney was yelling himself hoarse as he criss-crossed the state, looking considerably more relaxed, energetic and fluid on the stump than he has in months. He told the crowds "go out and vote… I need your help, and so does America".

He repeatedly laid out his five-point economic plan that he buttresses with the promise of 14 million new jobs - something some independent economists say that a recovering economy will provide irrespective of who is in the White House.

The opposition certainly knows there is suddenly that certain something about Romney. Getting voters to cast early votes and absentee ballots is a key part of the Obama campaign's complex on-the-ground effort, in a part a reflection of fears over Romney's building momentum.

After a fundraising surge, the Republican has a more impressive war chest ahead of the November 6 election - cash he will use in an advertising blitzkrieg in key states.

The panic was evident in an appeal to supporters sent from Vice-President Joe Biden yesterday. "Look - Barack and I need you," he wrote. "We recently found out that, as we head into the final push, Mitt Romney and the Republicans have $45 million more in the bank than we do."

The mood was palpable on the streets of Virginia, another swing state, at the weekend. "There's really something about Romney right now," said one Obama campaigner as he cornered shoppers in a Fairfax mall. "Frankly, we had it sewn up last time… this weekend I'm telling my friends that we've got to pull out all the stops if we are going to win this thing. It is whole different ball game."

Momentum, of course, is no platitude or cliché but part of the hard science of winning elections. It helps a candidate dominate a news cycle, even insulating them from potential brush fires that can threaten the weak or struggling contender.

In this case, the continued poll surges suggest Romney has avoided the flames from a scandal over remarks on abortion and rape from Republican Senate candidate Richard Mourdock. He has also avoided too much heat from the racially provocative remarks from Romney backer John Sununu over the endorsement of Obama by Republican and former secretary of state Colin Powell.

It also complicates Obama's efforts to highlight Romney's distortions and negatives, particularly his opposition to the successful bailout of the car industry - a big issue in Ohio.

Momentum, too, was in the minds of the Obama strategists who made the decision to launch a major advertising blitz early on, successfully shaping Romney's image as a cold, insincere former asset stripper before he had a chance to build his own appeal.

Under that pressure, he struggled for coherence all the way until the first debate, when Obama turned up with a unusually muted performance.

Just days before, Romney's campaign appeared to be degenerating amid reports of infighting and rudderless command.

"The Obama team had done a great job of telling the American people what Romney was like," one Washington Republican lobbyist said. "But then people tuned in to that first debate - and we're talking 67 million viewers - and saw Romney afresh, and liked what they were hearing."

Independent political scientist Charlie Cook noted that polls of undecided voters highlighted the unusual importance of the debates for Romney this time.

"The debates - I would say all three - hit a reset button for Romney and put him back into this contest," he wrote in the , adding the "horse race" still could go either way.

The Big Mo, in other words.