Read the US elections blog: Across the Pond

Mitt Romney is hemmed in on all sides by a crush of Iowans eating burgers and cameramen jostling for position, while he tries to edge his way past steaming plates of fried food to the centre of the diner.

He climbs on a chair, grabs a microphone, and swivelling from one part of the crowd to another, rushes through a truncated version of his stump speech, a simple menu of Ronald Reagan, values, patriotism and strong families. He shakes hands, signs autographs, grins a lot, and then jumps back on to the MittMobile campaign bus and on to the next event. He has been at the Hamburg Inn café in Iowa City for 25 minutes.

Mr Romney is a man constantly looking in different directions these days. Having spent millions of dollars of his own fortune to establish himself as the unassailable Republican candidate in Iowa and New Hampshire — the first two presidential nominating states — he is now locked in an increasingly ugly battle on both fronts, against two different rivals.

Unlike the Democratic presidential race, which is focused this week on the three-way battle in Iowa between Hillary Clinton, Barack Obama and John Edwards, the Republican contest has become an unpredictable two-pronged affair. Mr Romney, who is seeking to become America’s first Mormon president, is fighting Mike Huckabee for supremacy in Iowa and the resurgent John McCain in New Hampshire. The situation is forcing Republicans to shift their attentions from one snow-bound state to another, amid a flurry of attack ads.

Only two days before Iowa kicks off the nominating process, three polls suggest that Mr Romney has regained the initiative after losing his his lead to Mr Huckabee in November. He has clawed back to parity with the former Arkansas Governor after unleashing a barrage of negative advertising that he insisted was simply “pointing out our differences”.

Mr Huckabee, who has stumbled under the sudden glare of the front-runner’s spotlight, responded by accusing Mr Romney of running a “very desperate and frankly a dishonest campaign”.

Mr Huckabee, a Baptist minister whose surge in Iowa was based on the support of Christian evangelicals, acknowledged that Mr Romney’s attacks had hurt him. But he has also suffered from self-inflicted wounds, particularly on foreign policy, his greatest vulnerability. He expressed “our sincere apologies” after the assassination of Benazir Bhutto, before warning that America was in grave danger from Pakistanis entering the country as illegal immigrants.

Last night Mr Huckabee ordered his staff to pull an advertisement attacking Mr Romney - but only after it had been delivered to stations. Then, at a press conference, he played it for reporters anyway, a move that attracted widespread derision.

In New Hampshire, which votes five days after Iowa, polls place a rejuvenated Mr McCain in a statistical tie with Mr Romney. Mr McCain, who has fought his way back into contention after his campaign fell apart in July, is airing a commercial that highlights two newspaper “anti-endorsements” of Mr Romney, including one by the Concord Monitor calling him a phony. He says it was in response to attacks by Mr Romney on his record.

United by their common foe, Mr Huckabee and Mr McCain are also defending each other against Mr Romney. “I felt like when Mitt Romney went after the integrity of John McCain, he crossed the line,” Mr Huckabee said. “John McCain is a hero to me.” Mr McCain said: “He’s attacking Huckabee, who’s a good man.”

The bitter exchanges between Republicans are a function of an extraordinarily tight race that has had three different candidates leading opinion polls this month and where five — Mr Romney, Mr Huckabee, Mr McCain, Rudy Giuliani and Fred Thompson — have a realistic chance of winning the nomination.

Mr Giuliani, for a long time the national front-runner, is banking all on victory in Florida on January 29, before the delegate-rich states such as New York and California vote on February 5 — “Super Tuesday”.

A sixth candidate, Ron Paul, is expected to have raised $19 million in the past three months, surpassing most, if not all, of his better-known rivals. The 72-year-old libertarian and his committed band of internet activists could yet propel him to a fourth-place, or even third, finish in Iowa.

The difficulty picking a winner in the Republican contest reflects the growing tension within the party’s combustible coalition of fiscal conservatives, the Religious Right and national security hawks.

However, the biggest cloud hanging over both Democrats and Republicans is the prospect of the New York Mayor Michael Bloomberg stepping into the race as a centrist independent candidate able to fund a billion-dollar campaign from his own deep pockets.

On Sunday he will join Democratic and Republican elder statesmen for discussions about ending the gridlock between the two parties that characterises Washington politics.

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