Mike Huckabee's snatched victory from Mitt Romney in Iowa has thrown the Republican nomination for the presidency wide open and John McCain is now lining himself up to skewer Mr Romney in New Hampshire and, in effect, knock him out of the race.
New Hampshire's notoriously maverick voters are likely to be less impressed than the evangelical voters with the campaign of Mr Huckabee, the folksy Baptist preacher. Scenting blood, Senator McCain is on the rise and emerging as a real threat to Mr Romney who is hoping his credentials as former governor of neighbouring Massachusetts will stand him in good stead.
Romney, who outspent Huckabee by a factor of 20 to one in Iowa, was campaigning vigorously yesterday with more negative television ads blasting "Washington politicians" and their failure to halt illegal immigration. This was seen as a direct attack on Mr McCain who has moderate views on this key issue. Despite a shocking nine-point loss to Mr Huckabee, the Romney campaign sees Mr McCain as its biggest threat, but their candidate must bounce back quickly from the psychological blow of this opening caucus and, in just a few days, make his mark with the next state's Republican voters.
Rudy Giuliani's decision virtually to ignore Iowa and New Hampshire and concentrate on states with large populations that vote later is now looking questionable, and Mr McCain has surged forward as a leading contender for the nomination. The Vietnam veteran didn't canvas for votes in Iowa but still managed to garner 13 per cent of the vote. He is running on a ticket supportive of the war in Iraq, concerned about global warming and opposed to torture and Guantanamo Bay.
Up against a hugely well-resourced Romney campaign, Mr McCain has received a financial lifeline from his supporters and come back from near-bankruptcy in June to have enough money to buy expensive TV advertising in New Hampshire as well as the next Republican primary battlegrounds of South Carolina and Michigan. In June Mr McCain suffered a campaign implosion, and had to sack key advisers after running out of money.
New Hampshire is expected to be the key battleground, and local polling there shows nearly 40 per cent of Republican electors in the state are still undecided.
If Mr McCain loses on Tuesday, in the state where he famously beat George Bush by a margin of 19 points in 2000, he would have to fold his campaign.
Equally Mr Romney needs a win after a crushing defeat by Mr Huckabee in Iowa.
To lose the first two states in the primary season, after spending tens of millions of his own money on the campaign would signal the death knell of his White House race.