NASHUA, N.H. — Senator Obama, the new Democratic front-runner, told cheering supporters, “You’re the wave and I’m riding it.” Senator Clinton, her voice breaking, told voters in a little cafe that her White House quest is not just political.

“It is very personal for me,” she said in Portsmouth.

The presidential contenders hurtled toward tomorrow’s New Hampshire primary, tired, spent, and some still sniping at each other — hopefully or painfully aware of the stakes.

The top three Democrats criticized each other and two Republican candidates, Senator McCain and Mitt Romney, traded words with ever more bite.

Mr. Romney declared, “We need some voters,” one sentiment that could be embraced by all.

Mrs. Clinton and Mr. Romney suffered defeats in last week’s Iowa caucuses and are struggling to avoid a second major loss. Mr. McCain is surging on the Republican side, and polls show Mr. Obama leading for the Democratic primary here.

Fighting back, Mrs. Clinton questioned the substance behind the Illinois senator’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’s “Good Morning America,” Mrs. 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 criticizes 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. “What, as famously was said years ago, where’s the beef? You know, where is the reality?”

Later, during a meeting over coffee with undecided voters, a sympathetic voter asked how she keeps going. “It’s not easy,” she replied. “It’s not easy.”

“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.”

As for Mr. Obama, he had an enviable logistical problem. Hundreds of people couldn’t get into his speech at the Lebanon Opera House, so he addressed them with a microphone from the steps.

“You guys caught us a little by surprise,” he said. “You’re the wave and I’m riding it.”

Earlier, in Claremont, the long days seemed to be taking a bit of a toll on him — he flipped one of his signature campaign lines during a rally, saying, “The time for come has change.”

He also saw a doctor yesterday about losing his voice. The advice, Mr. Obama wryly told the audience in Claremont was “shut up.”

Mr. Obama challenged Mrs. Clinton’s claim in a weekend debate that he was raising “false hopes” about what he could deliver for the country. Mr. Obama told his audience that hope made President Kennedy aim to put a man on the moon and Martin Luther King to imagine the end of segregation.

“If anything crystalized what this campaign is about, it was that right there,” Mr. Obama said of Mrs. Clinton’s comment in the debate. “Some are thinking in terms of our constraints, and some are thinking about our limitless possibilities.”

John Edwards, running third in New Hampshire polls, showed no sign of flagging after a nonstop bus tour during which he gave speeches every couple of hours through last night and into this morning.

In a swipe at Mrs. Clinton, he said: “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.”

“There’s nothing illegal about it … but it is the status quo,” Mr. Edwards said.

Mr. Romney scheduled six events, an end-of-the-day rally and a two-minute television ad, while Mr. McCain pushed into what he called “The Mac Is Back” bus tour, flanked by dozens of friends and relatives who turned out for the final New Hampshire push. Optimism mixed with nostalgia as the Arizona senator sought a repeat of his surprise win here during his first White House run eight years ago.

“Tomorrow is the day when we will tell the world that New Hampshire again has chosen the next president of the United States,” Mr. McCain told a couple of hundred sign-toting supporters.

With his wife, Cindy, and two of their daughters behind him, Mr. McCain’s tone was a bit wistful at a chilly morning rally on the steps of the Nashua city hall. “There’s a lot of nostalgia associated with this morning. We’ve had a great time,” he said. “My friends, it has been an uplifting and wonderful experience.”

Iowa’s GOP winner, Michael Huckabee, said he wasn’t counting on winning a top spot in New Hampshire’s primary tomorrow. “If we come in anywhere in the third and fourth slot, we’re going to do great. I’d like to do better than that, but you have people who have had a lot more money spent here,” he told CNN.

The once front-running Mr. Romney was also circumspect about his chances.

“If I come in 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,” he said.

Mr. Romney’s first stop was the entrance of BAE Systems North America, where he found reporters and camera crews far outnumbered arriving workers. That prompted the former Massachusetts governor to exclaim, “We need some voters.”

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.

Told about Mr. Romney’s comments, Mr. McCain said, “I appreciate all those predictions about my political future, and I know they come from a vast storage of knowledge and background. … I’ll let the voters make a decision.”

Mr. Romney planned to air a two-minute television ad this evening, portraying Washington as in need of a president with the business and government background and experience that he has.

“It’s long past time to bring real change to Washington,” he says in the ad. “That’s never going to happen if all we do is send the same people back to Washington to sit in different chairs.”

A new survey showed Mr. Obama opening a wide lead over Mrs. Clinton, while the Republican race remained a statistical dead heat.

Mr. Obama had 41%, up from 32% in mid-December, in a new USA Today/Gallup poll. Mrs. Clinton was at 28%, down from 32%. Mr. Edwards had 19%, Governor Bill Richardson of New Mexico had 6%, and Rep. Dennis Kucinich had 3%.

On the Republican side, Mr. McCain had 34%, up from 27% in mid-December, while Mr. Romney had 30%, down from 34%. Mr. Huckabee was third with 13%, while Rep. Ron Paul of Texas and Mayor Giuliani were tied at 8%. A former Tennessee senator, Fred Thompson, who conceded yesterday he was focusing on South Carolina rather than New Hampshire, had 3%.

Both surveys had a margin of error of 4.4 percentage points, a small enough gap to consider the GOP race tied.

“Undeclareds” 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 favor of Mr. Obama, denying Mr. McCain the independent votes that catapulted him past President Bush in 2000.

Mr. Huckabee — and free pancakes — lured more than 400 people to tiny Mason, N.H., 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.

Mr. Huckabee encouraged voters to bring their friends and neighbors to the polls with them. But, he added, only if they supported him.

“If they’re not going to vote for me … let the air out of his tires. Shovel your snow into his driveway,” he joked. “Don’t let this person do damage to this country while you’re trying to do a good thing.”