Democratic presidential candidate Hillary Clinton battled to keep crucial New Hampshire from swinging to rising rival Barack Obama but new polls showed him jumping into the lead.

In the hotly contested Republican race, Arizona Sen. John McCain leaped ahead of former Massachusetts Governor Mitt Romney even as Mr Romney tried to raise doubts about Mr McCain.

New Hampshire's primary today is the next battleground in the state-by-state process of choosing Republican and Democratic candidates for November's election to replace President George W. Bush.

Republican candidates bickered over the Iraq war, illegal immigration and taxes in a Fox News Channel debate. Mr Romney and former Arkansas Governor Mike Huckabee, who won Iowa last week, accused each other of raising taxes in their states.

"Mike, you make up facts faster than you talk," Mr Romney told Mr Huckabee.

And Mr McCain accused Mr Romney of not raising questions about Mr Bush's war strategy when Defence Secretary Donald Rumsfeld was running it from 2003-06. Mr Romney replied he had a state to run at the time.

Mr Obama, an Illinois senator seeking to be the first black US President, built on his victory in Iowa last week with a significant bounce in New Hampshire, which votes today.

A USA Today/Gallup poll said Mr Obama had opened up a 13-point lead over Mrs Clinton in New Hampshire, 41 per cent to 28 per cent, to 19 per cent for former North Carolina Sen. John Edwards.

A WMUR/CNN poll showed Mr Obama leading Mrs Clinton, 39 per cent to 29 per cent.

Earlier polls had shown the race to be a dead heat between Mrs Clinton and Mr Obama.

A loss in New Hampshire would be a significant blow to Mrs Clinton in the New York senator's drive to become the first woman US president.

Trying to salvage New Hampshire, the former first lady engaged in some of her heaviest attacks against Mr Obama in the months-long campaign.

In Nashua, Mrs Clinton said that while Mr Obama talks a lot about changing the US, she believes she has actually carried out change. Change from the Bush administration is a leading theme in the presidential campaign.

"It is about how we bring about change by making sure we nominate and elect a doer and not a talker, that we begin to separate out rhetoric from reality," Mrs Clinton told a large, enthusiastic crowd in Nashua.

Accusing Mr Obama and Mr Edwards of not showing leadership on a litany of issues, she said, "That's not change," and the crowd joined in with her.

"That's not change," they yelled.

Mr Obama, at a rally at a high school in Salem, fired back: "We don't need our leaders telling us what we can't do. We need our leaders to believe in what we can accomplish."

The Clinton campaign also complained of the Obama camp making automated pre-recorded calls to New Hampshire residents who had registered on an official "do not call" list, a practice that would violate state law. The Obama campaign dismissed the complaint and said no law was broken.

The race was taking a negative turn on both sides in a state that is vital to efforts by Mrs Clinton and Mr Romney to revitalise their campaigns after disappointing showings last Thursday in Iowa.

Mr Obama received the endorsement of former New Jersey Sen. Bill Bradley, who finished a close second to then Vice President Al Gore in the 2000 Democratic primary here.

The USA Today/Gallup poll said Mr McCain had taken the lead over Mr Romney, 34 per cent to 30 per cent, with Mr Huckabee in third at 13 per cent.

A win for Mr McCain in New Hampshire would be a remarkable turnaround for him after his campaign suffered money problems last summer and was all but given up for dead.

Mr Romney, who would be the first Mormon President, needs to win or finish high in New Hampshire to maintain his credibility.

At a rally in Nashua, Mr Romney said he doubted Mr McCain would stand up well against Mr Obama, who he said was succeeding against veteran Democratic senators in the presidential race.