TILTON, N.H. — Republican presidential candidate Rick Santorum faced skepticism about his support for gun rights and engaged in a hostile exchange over gay marriage Thursday, all the while emphasizing a conservative record that he acknowledges is imperfect.
Santorum, who came within eight votes of winning Iowa's leadoff caucuses, is working to build a campaign machine, raise money and introduce himself to voters who had treated him as a footnote to this point. But as he has emerged as Mitt Romney's chief rival, he is drawing the scrutiny that comes with being at the front of the pack.
"What assurances can you give New Hampshire voters that you're not going to strip us of our Second Amendment rights?" one voter pointedly asked him in Tilton.
The voter cited Santorum's past endorsement of Arlen Specter, a former Pennsylvania senator who left the GOP and had supported restrictions.
Santorum said he was a supporter of gun owners' rights and took his son hunting during a recent trip to Iowa. He noted that he shot four birds on that outing near Des Moines, where he wore a high bright orange National Rifle Association hat. But he also acknowledged there were problems with his conservative bona fides, including his support of Specter, with whom he served in the Senate.
"Am I perfect? No. I've made mistakes and I've been upfront about that," he said, standing in a former train depot and addressing a standing-room-only crowd. That's become the new normal for a candidate who just weeks ago struggled to fill seats even in small venues.
His stark opposition to abortion and gay rights and his personal testimony of faith are central to his campaign. While that endears him to social conservatives, it won him a caustic reception at a conference in Concord for college students from across the country.
One man asked Santorum about his opposition to same-sex marriage, which is legal in New Hampshire. The candidate quickly picked a fight with the crowd, which seemed to support same-sex unions.
"So anyone can marry anyone else?" Santorum asked, swiftly turning the conversation to polygamy. "So anyone can marry several people?"
The crowd objected and tried to talk over him.
"I tried," he offered reporters as he left the conference center.
Santorum is making a hard, conservative play in New Hampshire despite its sometimes moderate electorate. He acknowledged New Hampshire's reputation but challenged its wisdom.
"Back in 1980, Iowa chose George H.W. Bush. New Hampshire chose Ronald Reagan," Santorum said, casting himself as the heir to Reagan and likening his rivals to Bush, whose moderate stances frustrated his party's conservative base.
Santorum's aides said he has raised $2 million in two days on the strength of his Iowa showing, and the campaign sought to show momentum by announcing the support of a New Hampshire tea party leader, a state senator, the head of a conservative think tank and Catholicvote.org, an online organization.
"And while no political candidate, or human being for that matter, is perfect, Rick Santorum's baggage contains his clothes," CatholicVote.org President Brian Burch said. "Republicans hoping to win back the White House in November must unite behind the candidate most dedicated to the foundational issues of faith, family and freedom."
A buoyant Santorum urged New Hampshire voters to make their own decisions, even as polls favor Romney as the Republican presidential standard-bearer.
"Don't settle for less than America needs," he said at the old train station here. "Don't defer your judgment to national polls. Don't defer your judgment to the pundits."
Romney, the former Massachusetts governor, eked out a victory in the Iowa caucuses and was favored to win the New Hampshire primary on Tuesday. But Santorum, carried by the momentum from his second-place Iowa finish, cast himself as the conservative best suited to challenge Obama.
"Our mission here is to show that we're the conservative alternative to Mitt Romney," he said in Manchester, virtually conceding he wouldn't be able to close a yawning New Hampshire gap in the polls.
"We were a mere 39 points behind Gov. Romney," Santorum said as he closed his day in Windham to an audience of more than 700. "I have a feeling we're not going to end up that way."
Associated Press Broadcast correspondent Sagar Meghani contributed to this report.