Republican White House hopefuls blitzed Iowa yesterday on the eve of its nominating caucus, with Mitt Romney hoping to turn a slight edge here into a lock on being the party’s champion against Barack Obama.

Dawn brought a last full day of frenzied campaigning before Iowans cast the first votes of what will be a year-long fight to the November 2012 elections, likely winnowing the field of candidates for the Republican nomination.

Mr Romney, a former Massachusetts governor and millionaire venture capitalist, has taken a thin lead in Iowa over veteran representative Ron Paul, while former senator and ardent social conservative Rick Santorum has surged to third place.

Mr Romney has made little secret that he hopes a first- or second-place showing in Iowa, followed by a win in New Hampshire one week later, and another in South Carolina after that, will let him win the nomination relatively early and focus his energies on the embattled Democratic president.

Mr Paul’s unorthodox libertarian views have earned him a devout following, but he is seen as uncompetitive in other states, while Mr Santorum faces an uphill fight to match Mr Romney’s massive national organization.

Public opinion polls have been more cruel to former House speaker Newt Gingrich, Texas Governor Rick Perry, and Representative Michele Bachmann, who said on Sunday that she hoped for a “miracle” in the heartland state’s in today’s caucus.

But those long-shot candidates still raced across Iowa, its famed cornfields barren and brown with the winter chill, mindful that surveys have found as many as four in ten likely voters say they could yet change their mind.

Unpredictable Iowa – where unemployment is well below the national average – is also an unreliable predictor of presidential fortunes: Senator John McCain, the eventual nominee in 2008, came in fourth that year.

But a victory in Iowa can lift a sagging campaign or give a top contender an extra air of inevitability, bringing fundraising dollars, endorsements and voter support that can shape the rest of the state-by-state nominating battle.

The caucus does not directly award delegates to the party’s summer nominating convention, but its first-in-the-nation status makes it a closely watched proving ground for the candidates’ appeal, organization, and ability to take or land a political punch.

Mr Romney’s massive campaign war chest and high-profile endorsements have fed his image as the candidate to beat – but he faces stubborn doubts about his conservative credentials and has been unable to increase his support among Republican voters nationwide above 30 per cent.