John McCain was declared the winner of the Republican primary in New Hampshire within an hour of polls closing overnight.
With less than half the votes counted, Mr McCain's opponents conceded the 71-year-old former prisoner of war's lead was unassailable.
John McCain winner of the Republican Party's New Hampshire primary
As more votes were counted ex-Massachusetts governor Mitt Romney was set to finish second with the winner of last week's caucus in Iowa, Mike Huckabee, in third.
Supporters at Mr McCain's campaign headquarters in New Hampshire chanted: "Mac is back" as the results of early counting emerged.
Mr McCain later emerged with his wife Cindy to tell supporters that his strategy was to "tell you what I believe".
"I'm past the age when I can claim the noun 'kid', no matter what adjective precedes it, but tonight, we sure showed them what a comeback looks like," he said.
His campaign was considered all but dead last summer as polls showed Mr Romney and former New York governor Rudy Giuliani running neck and neck far ahead of the Arizona senator.
Mr Giuliani, who has concentrated his campaign finances on other states finished fourth.
"This is the kickoff in what's going to be a very long and very tough game , but one that we're going to come out, and by the time it's over with ... we're going to be the nominee of the party," Mr Giuliani said.
Mr Huckabee, the Baptist minister whose Iowa rise was fuelled by support from religious conservatives. told supporters in Manchester, New Hampshire, that his campaign was far from over despite his third place showing.
"A few weeks ago we were way back in not so even sixth place and nobody thought that we would even be one of the contenders in New Hampshire. Tonight we're going to come out here with the continued momentum," he said.
Mr Romney, regarded as a model candidate who is still firmly in the race, was gracious in defeat, saying Mr McCain's team had run a "first-class race".
He failed to top the Republican poll for a second time despite being former governor of neighbouring Massachusetts and pouring tens of millions of dollars of his personal wealth into the campaign.
But after successive second places he insisted he had the credentials to inspire voters who want change.
"It's time to send someone to Washington who will actually get the job done. I don't think it's going to get done by Washington insiders," he said.
The race now begins to branch out quickly to more states, with Michigan voting next Tuesday, Nevada and South Carolina Republicans on January 19th.
Agencies