DURHAM, N.H. — Senator Obama yesterday made his debut appearance as a presidential candidate in the Granite State, following the same trail his leading Democratic rival, Senator Clinton, took just 24 hours earlier.

Mr. Obama spoke to about 100 New Hampshire residents in a modern, cedar wood home in Nashua roughly a mile from the house that hosted Mrs. Clinton on Sunday.

The guest lists at the two events, which included many of the same names, illustrated how hard the candidates are going to have work to woo support among the state’s voters, who are known to hold out before committing to candidates. The back-to-back campaign swings came as the candidates have begun clashing over the handling of the Iraq war.

Mr. Obama, who also received a raucous greeting from a crowd of about 3,000 people at the University of New Hampshire in Durham last night, told reporters that if the Senate had voted down the authorization of the Iraq war “we wouldn’t be in the situation that we’re in now.”

“As a consequence of that authorization, the administration was able to take this country down a path that has been, is very damaging for our national security,” he said. The comment was just one of several digs Mr. Obama has made at Mrs. Clinton — who voted to authorize the war, but has steadfastly called for an end to President Bush’s troop escalation — since officially declaring his candidacy over the weekend.

Meanwhile, Mrs. Clinton introduced a resolution in the Senate yesterday honoring the National Association for the Advancement of Colored People on the 98th anniversary of the organization.

The resolution is co-sponsored by 27 senators, but Mr. Obama, who is attempting to become the first African American president, is noticeably absent from that list. Mrs. Clinton’s office said all 99 of her colleagues were invited to sign on. Mr. Obama’s Senate staff could not be reached for comment last night.

While Mrs. Clinton faced tough questions on Iraq over the weekend, Mr. Obama was grilled for a second straight day about his recent comment that the country has seen the lives of 3,000 American troops “wasted” on a war that should not have been authorized. The Illinois senator yesterday again told reporters that he “would absolutely apologize” for the remark.

“It is not at all what I intended to say, and I would absolutely apologize if any of them felt that in some ways it had diminished the enormous courage and sacrifice that they’d shown,” he said.

At UNH last night, he causally answered questions in the school’s gymnasium in talk-show fashion, saying that “America has woken up” and touting the fact that he had been skeptical of claims of weapons of mass destruction from the outset. On Iran, he said America has to “use every diplomatic tool at our disposal” but that it should not “engage in blustery or overhyped threats based on ideology.”

While Mrs. Clinton traveled with a caravan of sport-utility vehicles, Mr. Obama showed up at the house of a state representative, Bette Lasky, in a Dodge minivan.

Another state representative, David Campbell, called Mr. Obama’s exit strategy for Iraq “the best thing I’ve heard so far.” When talking about those who voted to authorize the war, he said: “You have to question their ability to lead the country.”

“I would expect a presidential candidate and hopefully a president to have more vision than that,” he said. “There was a lot of Democrats sitting in front of their television sets watching that whole thing play out knowing it was the wrong move. And a lot of the leaders didn’t make the right move.”

A state executive councilor, Debora Pignatelli, who hosted Mrs. Clinton in her home on Saturday and attended yesterday house party with Mr. Obama, said she would “love to see a Hillary Clinton-Barack Obama ticket, or the other way around.”

When asked whether she had concerns about Mr. Obama’s lack of foreign policy experience, she said: “I wouldn’t be a concern before 9/11 for me. But it is a concern now. I think we do need people with experience who know how the game is played worldwide.”