Santorum's surge makes it a hollow victory for Romney

Frontrunner wins by just eight votes, while Michele Bachmann quits race after dismal showing

Rick Santorum cast doubt on Mitt Romney's chances of quickly sewing up the Republican presidential nomination after coming from the back of the field to tie the Iowa caucus vote, raising the prospect of a long and painful race.

After a long night that was full of suspense but short on clarity, party officials confirmed the split decision by Iowa Republicans. While Mr Romney had won Tuesday's caucuses, it was by a mere eight-point margin; he took 30,015 votes compared to 30,007 for the conservative Mr Santorum – 24.55 per cent versus 24.54 per cent.

In what will become a footnote of Grand Old Party history, a weak showing for the one-time front runner to challenge Mr Romney, and Tea Party favourite, Michele Bachmann, prompted the congresswoman to quit the contest entirely.

Wasting no time both men, as well as libertarian Ron Paul and former House speaker Newt Gingrich, who finished third and fourth in Iowa respectively, flew to New Hampshire which will hold the first fully-fledged Republican primary vote next Tuesday, setting in motion a string of state-by-state contests that will last six months. Also competing hard there will be Jon Huntsman, the moderate former governor of Utah.

Mrs Bachmann's announcement that she was dropping her bid was no surprise after she took just 5 per cent of the votes, a shocking collapse of support since winning the state's vaunted straw poll last August.

"Last night the people of Iowa spoke with a clear voice and I have decided to stand aside," she said.

There was muddle, meanwhile, over the intentions of Rick Perry, the Governor of Texas, who came in a poor fifth and told supporters he was going home to Austin to "assess" whether his campaign remained viable. Yet yesterday he indicated via Twitter that he intended to carry on, and aides said he would appear at two debates in New Hampshire this weekend.

While Mr Romney, who won the endorsement yesterday of Senator John McCain, the party nominee in 2008, had eked out his victory, the day belonged to Mr Santorum, a staunch social conservative and former Pennsylvania senator who staged a meteoric ascent in the last days of the caucus campaign. He will now present himself as the viable conservative alternative to Mr Romney.

Mr Santorum has scarce resources for the rest of the campaign and must compete still with Mr Gingrich and potentially Mr Perry, too, for the conservative votes. Further dividing the non-Romney constituency is Mr Paul, 76, whose libertarian stance, which includes isolationism on foreign policy and getting rid of the Federal Reserve, America's central bank, helped him win his third place in Iowa.

Mr Romney's share of the vote in Iowa was largely the same in 2008 when he eventually lost his nomination bid to Mr McCain. In Texas a cabal of high-powered conservative Republicans announced plans to meet next weekend to try to identify someone new to promote to derail Mr Romney.

The former Massachusetts governor, meanwhile, acknowledged that the attacks against him from all sides, including from Democrats, were about to intensify. "Look, I have pretty broad shoulders. I know the attacks are going to come – they're going to come more fast and furious now," he said.

Mr Huntsman, who has eschewed pandering to the party's right wing, will now see his campaign put on the line in New Hampshire, where he will try to present himself as the electable alternative who could appeal to moderate independent voters.