"Tonight, we made history," he exulted after becoming the first Republican non-incumbent presidential candidate since 1976 - when Gerald Ford won both Iowa and New Hampshire - to take the first two contests.
In second place, with 23 per cent, was the Texan libertarian Congressman Ron Paul whose support among young people has been consistently strong. Chants of "bring them home" broke out at the candidate's New Hampshire HQ as he warned that America could no longer afford to be the world's policeman. Jon Huntsman, the moderate former Governor of Utah who had devoted much of his scarce resources to New Hampshire, put on a brave face after coming third with 17 per cent. He insisted he would go on to the next contest in South Carolina on January 22 with a "ticket to ride".
Former House Speaker Newt Gingrich and former Pennsylvania Senator Rick Santorum - the surprise runner-up in Iowa - each had about 9 per cent. Texas Governor Rick Perry trailed with fewer than 2000 votes.
Romney blasted President Barack Obama and the "desperate Republicans" who had joined forces with him to "put free enterprise on trial". However his feisty comments will not eclipse his spectacular own goal in which he essentially handed a talking point to Obama's campaign. Throughout Tuesday and yesterday, Romney's Republican opponents attacked him for an unfortunate soundbite from a meeting in Nashua in which he told voters: "I like being able to fire people."
Never mind that he was talking about his preference to be able to switch health insurance, it gave further ammunition to Gingrich and Perry. Even as he held a baby in a throng outside a polling station yesterday, a person in the crowed yelled: "Are you going to fire the baby, too?"
Gingrich, in particular, has systematically accused Romney of basing his business success on the sacrifice of thousands of workers. One group of Gingrich's wealthy supporters known as a Super PAC has spent US$3.4 million ($4.3 million) on a 27-minute documentary, to air in conservative South Carolina, in which Romney is described as a "corporate raider". There has also been greater media scrutiny of Romney's stewardship of the private equity firm Bain Capital.
The frontrunner remains vulnerable to accusations that he is a policy "flip flopper" and new ads will attack his "pro-abortion" stance. His Mormon faith has caused soul-searching among the Christian evangelicals in his party.
The Gingrich barrage includes a spot attacking Romney for allegedly shifting positions on abortion. "What happened after Massachusetts moderate Mitt Romney changed his pro-abortion position to pro-life? He governed pro-abortion," an announcer says. "He can't be trusted."
Groups backing Romney have lined up a US$2.3 million campaign of their own for South Carolina. But his immense wealth is not necessarily an electoral advantage. A misjudged US$10,000 proffered bet to Perry during a televised debate only seemed to confirm criticism that he was out of touch with ordinary people. But yesterday, Romney simply shrugged off the "resentment of success".
Nationally, according to the latest Gallup poll, Romney is now the only candidate considered an "acceptable" nominee by a majority of conservative and moderate Republicans.
Yet the opinion polls show he would still lose in November against Obama, although the figures are tightening. According to a Reuters/Ipsos poll, Obama would defeat Romney by 48 per cent to 43 per cent, compared with 48 per cent against 40 per cent a month ago.
- additional reporting Independent