New dynamic for GOP as scene shifts to N.H.

Political observers said a crucial dynamic to watch in the coming week is whether former speaker of the House Newt Gingrich, who came in a disappointing fourth place in Iowa, will stay in the race partly to undercut Romney. Gingrich has praised Rick Santorum, the former Pennsylvania senator who was eight votes short of winning Iowa, while blasting Romney as a liar and a moderate.

Romney, fresh from his narrow victory in Iowa, bounded into the packed gymnasium at Manchester’s Central High School yesterday, accompanied by the man who defeated him in New Hampshire and won the Republican nomination in 2008, Senator John McCain of Arizona. McCain, who had said last year he didn’t intend to back anyone during the primaries, announced he was endorsing the man he repeatedly called “President Mitt Romney.’’

Romney implored New Hampshire voters not to become complacent, suggesting he needed a big win here. “It sure is nice to have a win, I tell you,’’ Romney said, referring to Iowa. “But the question I have for you is, Can we do better here in New Hampshire? I sure hope so.’’

The Iowa caucuses clarified the field overnight and put new power in the hands of New Hampshire voters to further shape the race. Michele Bachmann ended her campaign and Governor Rick Perry of Texas, who seemed ready to drop out, said instead he planned to campaign in South Carolina, which holds its primary after New Hampshire. The decision of both of those candidates created the potential that social conservatives here could rally around Santorum, helping him build upon his effort to become the alternative to Romney.

Romney “has really had an easy ride and I think that is now over,’’ said Linda Fowler, a government professor at Dartmouth College. “It isn’t just Gingrich in a grudge match. It is Ron Paul calling him a chameleon.’’

Paul, a libertarian representative, has run advertisements calling Romney a flip-flopper.

A series of contests within contests unfolded in the Iowa aftermath. Gingrich took out a full-page ad in the New Hampshire Union Leader in which he tried to define the primary as a race between him and Romney. Gingrich, who has been pummeled by advertisements from a super PAC formed by Romney’s friends, has said Romney is “not telling the truth’’ about his ties to the committee.

“The fact is three out of four Republicans rejected him,’’ Gingrich told reporters in Concord, referring to the Iowa results. “Governor Romney is a moderate Massachusetts Republican to the left of the vast majority of Republicans.’’

While Gingrich faces long odds in New Hampshire, analysts said he could have a significant impact by expending his resources and rhetoric against Romney. But it is not clear how much money he or his allies have. While Gingrich bought the Union Leader ad, he has not been a major presence in television advertising. A pro-Gingrich super PAC has posted an online ad but it is not clear whether the spot will run on television.

For all his tough attacks, however, Gingrich acknowledged that there was a limit to how far he would go in distancing himself from Romney. Asked by the Globe at a campaign event in Laconia whether he could ever vote for Romney for president, Gingrich said he could. That contrasted with Gingrich’s statement last month that he could not vote for Paul. “Romney is better than Barack Obama,’’ Gingrich told reporters. “There are huge weaknesses of Romney - I don’t think he can get elected. But if he’s the Republican nominee, I’ll support him.’’

He said Romney might not improve Washington, but Paul could bring harm to the country.

“Ron Paul’s position on Iran is a direct national security threat which could risk having millions of Americans die. This is not a game,’’ he said of Paul’s call to end sanctions and use diplomacy to preempt a crisis there. “He’s totally unrealistic about the nature of the Iranian regime and that fact that he doesn’t care if Israel gets wiped out is just unacceptable in a potential president.’’

While Paul has a loyal following here and hopes to do well, he made the unconventional decision to return to his home in Texas for a couple of days. He does not plan to be in New Hampshire until a rally tomorrow night in Nashua, according to his spokeswoman. But Paul’s presence is being felt in New Hampshire through his television ads attacking Romney.

Paul, who served as an Air Force surgeon, used an interview on CNN yesterday morning to attack Gingrich for not serving in the military. “When Newt Gingrich was called to service in the 1960s in the Vietnam era, guess what he thought about danger? He chickened out on that and got deferments and didn’t even go,’’ Paul said. “Right now he sends the young kids over there, and the young people come back and the ones in the military right now, they overwhelmingly support my campaign.’’

Gingrich, asked about the charge, responded, “I never asked for a deferment because during that period I was a father so it was automatic.’’

Romney tried to remain above the fray and focused on attacking President Obama. He acknowledged in an interview on MSNBC-TV’s “Morning Joe’’ that he had not paid much attention until recently to Santorum.

“We really haven’t had much opportunity to get to know Rick Santorum on the issues,’’ Romney said. “Over the past several months, our efforts have been focused on comparing and contrasting with Speaker Gingrich, with Rick Perry, with Herman Cain. These are the guys who have led in the polls.’’

Former Utah governor Jon Huntsman, who did not compete in Iowa, continued to stake his hopes on a strong finish here. His campaign launched a television ad that portrayed him as the best-prepared candidate and did not mention his rivals.

Kranish can be reached at kranish@globe.com. Follow him on Twitter @GlobeKranish. Matt Viser and Shira Schoenberg of the Globe contributed to this report.