MANCHESTER, N.H. — Her voice quavering, Sen. Hillary Rodham Clinton struggled Monday to avoid a highly damaging second straight defeat in the Democratic presidential race. Republicans John McCain and Mitt Romney scrapped for success on the eve of a New Hampshire primary that neither could afford to lose.

"You're the wave, and I'm riding it," Sen. Barack Obama, the new Democratic front-runner, told several hundred voters who cheered him in 40-degree weather after being turned away from an indoor rally filled to capacity.

Obama has been drawing large, boisterous crowds since he won the Iowa caucus last week, and a spate of pre-primary polls showed him powering to a lead in New Hampshire as well.

Clinton runs second in the surveys, with former Sen. John Edwards of North Carolina third, and the former first lady and her aides seemed to be bracing for another setback.

At one stop, she appeared to struggle with her emotions when asked how she copes with the grind of the campaign — but her words still had bite. "Some of us are ready and some of us are not," she said in remarks aimed at Obama, less than four years removed from the Illinois Legislature.

New Hampshire fairly crawled with candidates, so much so that at one point, McCain's three-bus caravan drove past Rep. Duncan Hunter of California, a long-shot Republican standing on a street corner with two other people waving to cars.

Opinion polls made the Republican race a close one between McCain, the Arizona senator seeking to rebound from last summer's near collapse of his campaign, and Romney, the former governor from next-door Massachusetts.

After sparring over taxes and immigration in weekend debates with McCain and former Arkansas Gov. Mike Huckabee, Romney cast himself as the Republican best able to hold the White House. "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," Romney said as he sped his way through a half-dozen events on a final full day of campaigning.

After first declining to predict victory in a state where he had led in surveys for months, Romney exuded confidence by the end of the day. "I'm convinced we're going to win tomorrow," he boasted at a rally for his staff at the campaign's headquarters. He attributed the change of heart to 100,000 telephone calls made by his staff, and his performance in back-to-back nationally televised debates on Saturday and Sunday.

McCain wasn't nearly as reluctant. "We're not gonna lose here," he boasted as he set out on a packed day of campaigning through seven cities. In a snow-draped setting in Keene, there seemed little doubt he had Romney in mind when he said voters would reject negative campaigning. "I don't care how many attack ads you buy on television," he said.

Romney has run several TV commercials against McCain in New Hampshire, arguing that the senator's immigration plan would offer amnesty for illegal immigrants and painting him as a disloyal Republican for twice opposing President Bush's tax cuts. McCain responded with an ad that includes a quote from The Concord Monitor that suggested Romney was a phony.

Obama won his Iowa victory on a promise of bringing change to Washington, trumping Clinton's stress on experience. She has struggled to find her footing in the days since, at the same time insisting she is in the race to stay.

Her husband, the former president, pointed out the obvious Sunday night in remarks before a college audience. "We can't be a new story," he said, speaking in something of a jocular tone. "I can't make her younger, taller, male."

Still, Sen. Clinton's aides have urged her to show more passion and emotion — including laughter — to give voters a sense of her warmer side.

By coincidence or not, she did so as she set out on a final day in New Hampshire.

"You know, I had so many opportunities from this country. I just don't want to see us fall backwards," she said at a morning campaign stop, her tone changing and voice quavering.

"You know, this is very personal for me. It's not just political. It's not just public. I see what's happening. And we have to reverse it."

Edwards criticized Clinton as ill-suited to bring about change. "The candidate — Democrat or Republican — who's taken the most money from drug companies is not a Republican. It's a Democrat, and she's in this race tomorrow morning," he said.

The ubiquitous polls suggested that independents would play a large role in determining the outcome of the Republican race.

Political independents accounted for 41 percent of the vote in the 2000 Republican primary in the state. McCain carried that group, 61-19, over George W. Bush and won the primary. Bush won the GOP nomination.

Now, eight years later, McCain again hopes to attract enough independent voters to defeat Romney.

But Obama's rise presents a challenge McCain didn't face in 2000. The Illinois senator showed strong appeal among independents in Iowa, and pre-primary polling in New Hampshire indicates he is poised to gain substantial backing there as well.

That left McCain contesting Obama for independents and Romney for Republicans as he worked to climb back into the race after his campaign nearly imploded last summer. At the time, he was struggling to defend the Iraq war, unpopular with independents, and linked to an immigration position that drove away conservatives. In the months since, he has worked to take the edge off the immigration issue, and the war has receded as a campaign concern as U.S. casualties have declined.

Huckabee, the former Arkansas governor, flipped pancakes Monday in a state known for its maple syrup and struck a tone that was both populist and conservative.

"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 in a pitch aimed at independent voters. Speaking to conservatives, he added, "I have also heard folks say people in New Hampshire don't care about issues like family and the sanctity of life. I'd beg to differ."

He finished first in the Iowa caucuses last week on the strength of support from evangelical conservatives, but Tuesday's today's primary appears to offer far less prospect of success.

With the two parties still picking their candidates for the fall, New York Mayor Michael Bloomberg participated in a meeting devoted to bipartisanship, stirring renewed speculation that he will run as an independent.

"People have stopped working together, government is dysfunctional, there's no collaborating and congeniality," said the mayor, who has said several times he does not intend to seek the White House.

Contributing: Charles Babington, Beth Fouhy, Sara Kugler, Jim Kuhnhenn, Nedra Pickler, Libby Quaid, Beverley Wang and Glen Johnson