An overflow of supporters cheered Barack Obama today as polls showed the Illinois senator was poised for a second unexpected victory over Hillary Rodham Clinton in a week.
"You're the wave and I'm riding it," Mr Obama said as the presidential contenders hurtled toward Tuesday's New Hampshire primary.
Trying to revive her campaign, Ms Clinton declared: "Whatever happens tomorrow, we're going on."
Senator Hillary Clinton talks to supporters preparing to canvass for her in Manchester, New Hampshire yesterday
Republican Mitt Romney worked furiously to avoid a second defeat after his poor showing in Iowa last week.
Ms Clinton and Mr Romney suffered defeats in last week's Iowa caucuses and are struggling to avoid a second major loss tomorrow. John McCain is surging on the Republican side.
A new survey showed Mr Obama opening a wide lead over Ms Clinton, while the Republican race remained a statistical dead heat.
Fire marshals from Manchester south to Salem and east to Exeter had to shut the doors to each of Mr Obama's five rallies on Sunday, as crowds flocked to see the Illinois senator who took a step last week towards becoming the first black president with a decisive win in the Iowa caucuses.
Ms Clinton, the New York senator and former first lady trying to become the first female president, took to the airwaves with television interviews in which she questioned the substance behind Mr Obama's soaring rhetoric.
She said Mr Obama "is a very talented politician" but is not living up to his claim to be a new type of politician.
Interviewed on ABC television's Good Morning America, Ms Clinton pointed out that Mr Obama has portrayed himself as being outside the influence of special interests yet picked a New Hampshire lobbyist to co-chair his campaign in the state. She also accused him of changing positions on issues, even though he criticises other candidates for the same thing.
"All of a sudden you start to ask yourself, Wait a minute. I mean, what is the substance here?" she said.
Asked on CBS television's The Early Show whether the Iowa defeat indicated that voters were disenchanted with her and wanted to move on, Ms Clinton said: "I'm just going to work as hard as I can today and tomorrow ... I feel really good about this whole process, and you know, whatever happens tomorrow, we're going on."
In a last-minute pitch for votes later today, Ms Clinton's eyes welled up and her voice broke repeatedly as she talked with supporters in a restaurant in Portsmouth.
"I've had so many wonderful opportunities in this country," she said, her voice catching. "This is very personal for me. It's not just political. It's not just public."
On the Republican side, Mr Romney had banked on victories in Iowa and New Hampshire to propel his campaign forward, but was defeated last week in Iowa by rival Mike Huckabee, the Baptist preacher-turned-politician who swept past him with an underfunded campaign. Now Mr Romney faces a strong challenge from a resurgent Mr McCain in the first-in-the-nation primary.
After a speech to employees at the Timberland shoe company in Stratham, Mr Romney argued that Mr McCain would not be the best candidate to compete against a Democrat such as Mr Obama.
"I think Barack Obama would be able to do to John McCain exactly what he was able to do to the other senators who were running on the other side" in Iowa, he said.
Mr McCain set off on a seven-city swing dubbed "The Mac Is Back" bus tour, flanked by dozens of friends and relatives. Optimism mixed with nostalgia as the Arizona senator sought a repeat of his surprise win in the New Hampshire primary during his first White House run eight years ago.
"There's a lot of nostalgia associated with this morning. We've had a great time," Mr McCain told a couple of hundred sign-toting supporters. "My friends, it has been an uplifting and wonderful experience."
Mr Huckabee said today he was not counting on winning a top spot in New Hampshire's primary. Overwhelming support from evangelicals cemented his Iowa victory, and he was not expected to find those votes in the north-eastern state.
Still, he lured more than 400 people to the tiny town Mason this morning to hear his populist economic message. The crowd had to be divided into two seatings to hear Mr Huckabee and his campaign sidekick, actor Chuck Norris.
"The reason our campaign is getting lots of folks just like you out there with energy and enthusiasm is because there's a great need in this country to elect someone who reminds them of the guy they work with, not the guy who laid them off," he said. "That's why our campaign is getting deep roots even in New Hampshire where folks said 'Huckabee will never draw a crowd'. Well, a few people came out here today."
A new USA Today/Gallup poll showed that 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. Mr Huckabee was third with 13 per cent, while Rep Ron Paul of Texas and former New York mayor Rudy Giuliani were tied at 8 per cent. No other candidate, including former Tennessee Sen Fred Thompson, who conceded on Sunday he was focusing on South Carolina rather than New Hampshire, was above 3 pre cent.
On the Democratic side, Mr Obama had 41 per cent, up from 32 per cent in mid-December. Ms Clinton was at 28 per cent, down from 32 per cent. Former North Carolina Sen John Edwards had 19 per cent, New Mexico Gov Bill Richardson had 6 per cent, and no other candidate had 3 per cent.
Both surveys had a margin of error of 4.4 percentage points, a small enough gap to consider the Republican race tied.