Hillary Clinton came close to tears during a campaign stop in New Hampshire as new polls showed her trailing Barack Obama on the eve of the crucial state primary.

At a coffee shop in Portsmouth, Mrs Clinton became emotional when asked by a woman voter: “How do you keep upbeat and so wonderful?”

After beginning her answer, her voice began to break and tears filled her eyes. “You know, this is very personal for me. It’s not just political it’s not just public. Some people think elections are a game, lot’s of who’s up or who’s down, [but] it’s about our country.”

Polls show Mr Obama is set to claim another emphatic victory in New Hampshire's Democratic primary today following his success in Iowa last week. He told ecstatic supporters at another packed rally: "You're the wave and I'm riding it." Later, he told a TV interview: "We obviously started something, now we've got to finish it."

He challenged Mrs Clinton's claim that he was raising "false hopes" for the country, citing the way John F Kennedy told America to reach for the Moon or Martin Luther King dreamt about ending racial segregation.

"If anything crystalised what this campaign is about, it was that right there," he said. "Some are thinking in terms of our constraints and some are thinking about our limitless possibilities."

John Edwards, running third in the polls, is hoping a knockout blow to Ms Clinton could give his Democratic candidacy the legs it needs to continue beyond New Hampshire. On a non-stop bus tour through the Granite state, he repeatedly swiped at her, saying she had taken more money from pharmaceutical companies than any other candidate - Democrat or Republican.

Mr Obama's sudden rise to the ascendancy in the race has left the Clinton campaign reeling, with aides having to deny that she would pull out if her money dries up and her standing in polls continues in freefall.

Mrs Clinton continued to criticise Mr Obama for lacking experience and being more words than action. "Wait a minute," she said, "what is the substance here? What, as famously was said years ago, where's the beef? You know, where is the reality?" At an earlier event, she took aim at his grandiloquent claims to be a man trying to unite America and bring a decisive break from the Clinton and Bush years. She said: "You campaign in poetry, you govern in prose."

Most observers believe a second heavy defeat for her in New Hampshire would make it very hard for her to stage a recovery before Super Tuesday on February 5 when when many of America's most delegate-rich states will vote.

A USA Today/Gallup poll put Mr Obama's support at 41 per cent, up from 32 per cent in mid-December. Mrs Clinton was at 28 per cent, down from 32 per cent. Mr Edwards had 19 per cent, while New Mexico Governor Bill Richardson had 6 per cent.

The stakes were also sky-high in the Republican race where almost half a dozen candidates can still make a credible claim for the nomination. Mitt Romney, who has seen his long-standing poll lead in New Hampshire overtaken by resurgent John McCain, scheduled six events yesterday.

He appeared to downplay expectations, saying: "If I come in a second-place finish, that will actually say that I am clearly one of the leading contenders. I will have come in second in Iowa, first in Wyoming second in New Hampshire. That will mean that I probably have more votes than anybody else in those first three states."

At his first stop of the day, at the entrance to BAE Systems North America, members of the media outnumbered workers. "We need some voters," said the former Massachusetts governor.

Later, he one again donned the mantle which has been worn to such effect in the Democratic race, predicting that Mr McCain, as a long-standing Senator, would fall victim to Mr Boatman's call for change in a general election face-off. Independent voters make up the majority of registered voters in the state and they are free to vote in either primary tomorrow. Romney aides hope for a surge in favour of Mr Obama, denying Mr McCain the votes that catapulted him to a New Hampshire win in 2000 against George Bush.

Mr McCain pushed on into what he called "The Mac Is Back" bus tour. With his wife, Cindy, and two of their daughters behind him, he said on the steps of Nashua city hall: "There's a lot of nostalgia associated with this morning. We've had a great time. My friends, it has been an uplifting and wonderful experience."

When informed of Mr Romney's comments, he replied with barbed sarcasm. "I appreciate all those predictions about my political future," he said, "and I know they come from a vast storage of knowledge and background."

Mike Huckabee, who won the Republican caucuses in Iowa suggested he would be satisfied with "third or fourth slot" in New Hampshire where the Evangelical Christian voters who propelled him to victory last week are in much shorter supply.

One poll put support for Mr McCain had 34 per cent, up from 27 per cent in mid-December, while Mr Romney had 30 per cent, down from 34 per cent. Mike Huckabee was third with 13 per cent, while maverick Ron Paul and former New York mayor Rudy Giuliani were tied at 8 per cent. No other candidate, including Fred Thompson - who conceded on Sunday he was focusing on South Carolina - was above 3 per cent.

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