NASHUA, N.H. -- Former Massachusetts Gov. Mitt Romney, once a frontrunner here, is fighting for his political life.

After months of intense campaigning and millions of dollars in spending, the Republican landed in a disappointing second place in his party's Iowa caucuses last week.

Now several polls in New Hampshire, which holds the nation's first 2008 presidential primary election tomorrow, show him consistently trailing Sen. John McCain, R-Ariz.

A USA Today/Gallup Poll released yesterday put Mr. McCain four points ahead of Mr. Romney.

"I will win," the senator boldly predicted, according to The Associated Press.

A weak performance in the primary could cripple Mr. Romney's well-funded, well-organized campaign, although some top supporters and advisers are playing down such a scenario.

"He is the only guy who is going to finish in first or second in both Iowa and New Hampshire. That's a plus," said GOP Sen. Judd Gregg, who, as a member of one of New Hampshire's most powerful political families, has endorsed Mr. Romney.

The candidate himself delivered a similar message on the trail yesterday, telling a crowd in the Elm Street Middle School in Nashua that finishing behind former Arkansas Gov. Mike Huckabee in the caucuses, but ahead of Mr. McCain and former Sen. Fred Thompson of Tennessee, was a sign that voters are looking for new faces in Washington, D.C.

He even touted Sen. Barack Obama's win over Sen. Hillary Rodham Clinton on the Democratic side as proof of his own electability on the national stage.

"Americans are not looking for Washington insiders," he said. "They're looking for change and change is what we're going to give them."

Yet Mr. Romney sunk significant resources into both Iowa and New Hampshire, hoping that back-to-back victories would raise his national profile and set him on the path to the nomination. He far outspent Mr. Huckabee, who was barely registering in Iowa polls just a few months ago.

Here, he's spent nearly $4 million to run advertisements on WMUR-TV, the only statewide commercial station, according to a Web site maintained by Dante J. Scala, a professor of political science at the University of New Hampshire. That sum has bought him 3,600 commercials since February.

Mr. McCain, who has struggled to raise money consistently during this election cycle, has spent $1.1 million at WMUR.

Thomas D. Rath, a senior adviser to the Romney campaign and a former New Hampshire attorney general, argued that Mr. McCain, the winner of the 2000 Republican primary here, needs to win again to have any chance of moving on, while Mr. Romney has the resources to keep running.

"We want to win New Hampshire," Mr. Rath said. "The real person who has to win is McCain."

Yet victory in New Hampshire has been a right of passage for Massachusetts politicians seeking the presidency. John F. Kennedy, former Gov. Michael Dukakis and Sen. John F. Kerry all won here before taking the Democratic nomination. In 1980, Sen. Edward Kennedy lost, and the nomination went to President Jimmy Carter.

(In 1964, former Sen. Henry Cabot Lodge Jr. of Massachusetts, then U.S. ambassador to South Vietnam, won New Hampshire's Republican primary as a write-in candidate, but Sen. Barry Goldwater of Arizona went on to win the party's nomination that year.)

Even if he falls short tomorrow, Mr. Romney will be a strong contender in Michigan's Jan. 15 primary. His father, George W. Romney, was the state's governor from 1963 to 1969. But the following two contests -- in South Carolina and Florida -- could be out of reach.

His GOP rivals appear to sense weakness. During a debate at New Hampshire's St. Anselm College on Saturday, they took turns attacking the former governor.

"We disagree on a lot of issues, but I agree you are the candidate of change," Mr. McCain said with a chuckle, reminding viewers that Mr. Romney has moved to the right on major issues, including abortion.

Former New York City Mayor Rudy Giuliani said even President Ronald Reagan, a revered figure among the GOP base, would have been the target of "Mitt's negative commercials."

At a forum sponsored by Fox News last night, Mr. Rommey sparred with Mr. Huckabee over their records on taxes.

"Mike, you make up facts faster than you talk," he told his fellow former governor.

Mr. Huckabee responded: "You spent tens of millions of dollars saying all negative things about me. If someone raises a question, you say it's a personal attack."

Both on the trail and on television, Mr. Romney has been playing defense and offense simultaneously, attacking Mr. McCain's support for a broad immigration bill last year and his opposition of President Bush's 2001 tax cuts.

"He's simply wrong," Mr. Romney said. "He's consistent, but he's wrong. And I'll take being right over being consistent every day of the week."

Mr. Romney's supporters seemed to appreciate his stance.

"Everybody changes their views and thoughts in life," said Thomas Trimarlo Jr., 41, who moved from Massachusetts to New Hampshire two years ago to work for H.J. Heinz Co. here. "I don't think he did it to become president."

But Mr. Trimarlo acknowledged that a lot is at stake for the candidate tomorrow.

"Being so close to Massachusetts," he said, "it wouldn't look good if he lost."