He has been mocked as rich and out of touch, struggled to woo his own party and left a trail of gaffes -- but Mitt Romney still has a genuine shot to make Barack Obama a one-term president.

A cascade of new polls, uncertain economic data and fresh concern that Europe's woes could cross the Atlantic, point to the Republican's best chance of beating Obama in November -- dismay about America's slow economic recovery.

Though Obama is ahead by a nose despite the slowest recovery in decades, the president has little breathing room should the economy slow this year, as it did in 2010 and 2011.

Voters seem to like Obama more and believe he cares more about the middle classes, according to early polls ahead of the November 6 election.

So, should the rebound maintain a pace that has created around million jobs over five months, and if Obama navigates sudden crises at home and abroad, he looks well placed with his approval rating approaching 50 per cent.

Yet polls suggest voters are not yet feeling the economic recovery, or Obama's strategy to create jobs -- giving Romney a fungible, yet genuine opening.

A slowing of the pace of job creation, to just 120,000 positions, in March, has fueled fears the recovery could be stalling. Europe's woes are again worrying US investors.

Major polls now show the Romney and Obama matchup largely within the margin of error.

In a Wall Street Journal/NBC poll this week, Obama led Romney by 49 per cent to 43 per cent. The New York Times/CBS survey had them pegged at 46 percent and a Quinnipiac University poll had the president up 46 to 42 per cent.

"I think if the election were held today it could go either way," said Bruce Buchanan, a professor of government at the University of Texas.

"On eight out of ten days, Obama wins by one point if everything is as it is right now. But bad news at the wrong time could turn it into a five point loss for the president."

Polls suggest Romney has started to unite his party after a divisive primary fight and reveal America is still a nation split down the political middle.

"This is going to be a very very close election We are not going to win it 54 to 46 (percent) -- it is going to be very close," said a senior White House official. Obama clearly has cause for concern over the economy.

Only 38 per cent of those asked in the Journal poll thought the economy would get better in the next year, and the president's economic approval rating was under water at 45 per cent.

The Times poll had Obama's approval rating on the economy at 44 per cent. Quinnipiac had voters preferring Romney to deal with the economy, create jobs and bring down a spike in gasoline prices.

Thomas Baldino, a professor of politics at Wilkes University, Pennsylvania, believes that if the election were held now, Romney could win as many Americans simply do not feel their financial situation improving.

He warned that a torrent of advertising expected from Romney and allied special interest groups could shred Obama's political message.

"Unless there is something tangible for people to look at and feel that the economy has improved, then those negative ads are going to make it difficult for Obama to say he is the guy to turn around the economy."

Romney has plenty to worry about too. Though he leads Obama among white voters, he trails badly among the vital voting blocs of women and Hispanics -- by margins that guarantee a loss if he cannot close the gap.

Romney has anchored his assaults against Obama on the economy under the slogan 'Obama Isn't Working'.

But if unemployment ticks down from the current 8.2 per cent, Obama's advantages elsewhere may be decisive.

The superior Obama campaign machine will meanwhile seek to exploit Romney's reputation as a corporate raider who made a fortune sometimes at the expense of other people's jobs.

Obama is implicitly also attacking Romney's wealth, campaigning for higher taxes on the rich as his surrogates demand his rival open his tax records for inspection.

Romney also starts from behind on the electoral map which candidates mine for 270 electoral votes needed to be president.

Obama has more routes to victory, while Romney cannot afford to lose battlegrounds like Florida and Ohio and still hope to reach the White House.

And Romney must also conquer conventional wisdom, which doubts his skills as a candidate and chances of victory -- a feeling that the Politico website reported Friday extends to members of his own Republican Party.