MANCHESTER, N.H. — Senator Clinton, Democratic presidential front-runner no longer, accused Senator Obama of changing his positions on health care and “a number of issues” last night in a debate three days before the New Hampshire primary.

“I have been entirely consistent in my position,” Mr. Obama countered, adding that he and Mrs. Clinton have a philosophical disagreement over her proposal to require Americans to purchase health insurance or face a penalty from the government.

Mr. Obama won the kickoff Iowa caucuses Thursday, and his remaining rivals — Mrs. Clinton, a former senator, John Edwards, and Governor Bill Richardson of New Mexico — can ill afford for him to gain a victory in New Hampshire’s first-in-the-nation primary as well.

“You said you would vote against the Patriot Act. You came to Senate, you voted for it. You said you would vote against the Iraq war, you came to the Senate and voted for” funding, she said.

“I think we should get into examining everybody’s record,” she said.

Mr. Obama’s candidacy has soared on his pledge to bring change to Washington, and Mrs. Clinton sought to blunt his advantage while sticking to her own campaign-long theme. “I have 35 years of experience making change,” she said.

Mr. Edwards, second-place finisher in Iowa, worked throughout the debate to align himself with Mr. Obama as an advocate for change in Washington, and described Mrs. Clinton as a defender of the status quo. “Every time he speaks out for change, every time I fight for change, the forces of status quo are going to attack,” Mr. Edwards said.

“I didn’t hear these kind of attacks from Senator Clinton when she was ahead,” he said. “Now that she’s not we hear them.”

There were a few moments of humor.

“I’ve been in hostage negotiations that are a lot more civil than this,” Mr. Richardson, a one-time diplomat, said at one point.

Asked what she could say to voters who don’t find her likable enough, and seem to like Mr. Obama more, Mrs. Clinton drew laughter. “Well, that hurts my feelings. … But I’ll try to go on.”

She said she agreed that Mr. Obama was likable, then added, “I don’t think I’m that bad.”

That drew a wry response from Mr. Obama, who said, “You’re likable enough, Hillary.”

The debate unfolded as a new poll showed a close race between Clinton, the one-time national front-runner, and Mr. Obama. Her aides debated privately how forcefully to attack her rival, and the campaign distributed a mass mailing that criticizes him for voting present on legislation while he served in the Illinois Legislature, rather than in favor of measures backed by abortion rights groups.

With the first primary only three days away, the former first lady had little time to make the case she hoped would knock Mr. Obama off stride.

Challenged on health care, Mr. Obama acknowledged that he has said if he were designing a system from scratch, he would set up a single-payer system that would give coverage to all. He said that is impractical, given the current system in which so many people receive their insurance from employers.

Mr. Obama’s health care plan relies on government financial incentives and cost-cutting to help the uninsured afford coverage. But unlike Mrs. Clinton and Mr. Edwards, he does not require adults to buy coverage or pay a penalty if they fail.

“I disagree with that because as I go around, I don’t meet people who avoid getting health care. The problem is they can’t afford it,” he said.

The opening moments of the debate produced agreement on Mr. Obama’s summertime statement, controversial at the time, that he would take action against a terrorist leader, Osama bin Laden, if he had actionable intelligence that he was hiding in Pakistan and the government there did not act.

“As much as possible,” America should seek agreement from Pakistanis, Mr. Obama added.

Mr. Edwards agreed. “If I as president of the United States know where Osama bin Laden is I would go get him,” the 2004 Democratic vice presidential nominee said.

Likewise, Mr. Richardson said that if diplomacy failed and the Pakistani government was incapable of moving against the terrorist leader, “then you do take that action.”

Mrs. Clinton agreed, saying, “At some point, probably when the missiles have been launched, the Pakistani government has to know they are on the way.” She said that was important to make sure Pakistan didn’t jump to the conclusion that it was under attack from India, its longtime rival in southwest Asia.

During campaigning yesterday, a noticeably more freewheeling Mrs. Clinton subtly likened Mr. Obama to Democratic nemesis President Bush while Mr. Edwards mocked the idea of a nice candidate bringing change.

Mr. Edwards hinted he would welcome a second-place finish to Mr. Obama, which advisers said they hoped would turn the contest into a two-man race and take Mrs. Clinton out of the game. Mr. Edwards narrowly edged Mrs. Clinton for second place in Iowa, which he couched as an upset that he would be happy to replicate here.

What happened Thursday in the Iowa caucus “is going to happen here in New Hampshire,” Mr. Edwards told an overflow crowd at Lebanon High School auditorium. Even though he effectively acknowledged he wouldn’t win the state, he was relaxed and playful, shucking his suit jacket after the speech and shooting hoops with his shirt tail hanging out while the crowd applauded.

The debate was sponsored by ABC News and Facebook.