The Republican presidential underdog Senator John McCain of Arizona, soundly defeated the front-runner Mr George W Bush, the Governor of Texas, yesterday in the New Hampshire primary while Democratic rivals Vice-President Al Gore and former Senator Bill Bradley were fighting a close battle.
Mr McCain won the first-in-the-nation primary by a wide margin over Mr Bush, according to television projections based on exit polls.
These early projections suggested Mr McCain would win by a double-digit margin. Such a result would damage Mr Bush's aura of invincibility and tighten the contest for the Republican presidential nomination over the next several weeks.
Among Democrats, Mr Gore was locked in a tight battle with former Senator Bradley of New Jersey. Polls had predicted an easy victory for Mr Gore but a huge turnout of independent voters unaligned with either party, tightened the race.
Exit poll projections showed the race was too close to call immediately.
The stakes were huge for Mr Bradley, who appeared to have closed the gap with a furious assault on Mr Gore's honesty and trustworthiness over the final week of the campaign.
If he were to win, the former basketball star has five weeks to take his insurgent campaign to the next level. There are no Democratic primaries until March 7th, when 16 votes, including New York and California, vote.
Just before the polls closed in New Hampshire, Mr Bradley challenged Mr Gore to hold weekly debates, starting on Sunday, leading up to what he called the "national primary".
The Republicans have several primaries in February, including Delaware, Michigan, Virginia and Arizona. But the next big battle is in South Carolina on February 19th.
Three other Republican candidates - Mr Steve Forbes, Mr Alan Keyes and Mr Gary Bauer - trailed far behind. Mr Bauer, a conservative activist running on a strong anti-abortion platform, seemed likely to pull out soon.
The Texas governor remained the overwhelming choice of the party establishment. But Senator McCain's victory was expected to raise doubts throughout the party about Mr Bush's strength as a presidential nominee.
"The margin is very important. If it's a double digit win for McCain, that would be substantially more damaging for Bush than if it stayed in single digits," a pollster said.
Mr Bush sounded resigned as he stepped into the early morning cold, canvassing voting stations.
"It's a marathon, it's a long haul. I'm a patient man," Mr Bush told reporters.
"I've got the discipline and I've got a view for the future so I'm ready for what comes . . . I am going to the next state and the next state and the next state until I win my party nomination and then I'm going to unite our party and lead us to victory," he said.
Mr McCain still faces long odds against Mr Bush, who possesses a formidable national organisation and a huge money advantage. South Carolina, the state on which Mr McCain is now pinning his hopes, has a tradition of backing the front-runner in Republican primaries.
"South Carolina has ultimately always endorsed the mainstream candidate," a political scientist formerly of the University of South Carolina, said. But a big McCain victory might prompt rank-and-file Republicans, who are desperate to find a winner who could take back the White House after eight years of Democratic control under President Bill Clinton, to reassess Mr Bush's prospects.
If Mr Gore was to eke out a win in the Democratic primary, Mr Bradley's prospects would suffer a grievous blow.
The former senator has plenty of money to continue the fight, but he trails Mr Gore in national polls by a wide margin and lacks the vice-president's institutional support from labour unions and party activists.
