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Mitt Romney eked out the narrowest of victories in Iowa over Rick Santorum and now may have to ward off a combined onslaught from his rivals in the Republican presidential primary race, despite holding a sizable lead in the next voting grounds of New Hampshire.

The former Massachusetts governor has been accused of going negative on Newt Gingrich, and while Gingrich ranked a distant fourth in Tuesday's Iowa caucuses, he is firing up to return the attack, while still maintaining the claim he is engaging in a positive campaign.

Gingrich told radio host Laura Ingraham on Wednesday that he could see himself and Santorum try to double-team the former Massachusetts governor, who with an expected endorsement on Wednesday from Sen. John McCain, effectively becomes the "establishment" candidate.

"Rick and I have a 20-year friendship, we are both rebels, we both came into this business as reformers, we both dislike deeply the degree to which the establishment sells out the American people," he told Ingraham.

"We both think Washington has to be changed in very fundamental ways, and we have lots of things that fit together. And the thing that's interesting is if you take the votes, you add to that (Rick) Perry and (Michele) Bachmann, you begin to see the size of the conservative vote compared to Romney ... if you take, you know, Santorum and Perry and Bachmann and Gingrich you get some sense of what a small minority Romney really represents," Gingrich said.

Santorum has not yet indicated whether he would form an alliance with the former House speaker, saying on Tuesday night in a speech to supporters that he's better prepared for New Hampshire than his rivals or the political class think.

"You think I've been in Iowa a lot. I've been to New Hampshire 30 times and have been more times and done more events than anybody but Jon Huntsman. And 'he cheats; he lives there,"" Santorum said in reference to Romney.

"We will be in New Hampshire. We'll leave tomorrow. We'll spend our time there. And with your help and God's grace, we'll have another fun night a week from now," he told supporters in Iowa.

Gingrich too took an early flight to New Hampshire on Wednesday, leaving just before midnight and shortly after railing against negative ads that he blames for pushing him into fourth place in Iowa. Gingrich said he's not going to go negative in response, but he won't back down from using the truth as a defense -- or an offense.

"Let me be clear, because I think it's important, given all the things that were done in this state over the last few weeks," he told supporters. "We are not going to go out and run nasty ads. We're not going to go out and run 30-second gotcha -- we're not. But I do reserve the right to tell the truth."

In his concession speech and in an ad in a New Hampshire newspaper, Gingrich called himself a "bold Reagan conservative" versus "a timid Massachusetts moderate." He said that he thinks Romney may be good at "managing the decay" in Washington but doesn't have the ability to turn around a broken system.

The growing animosity between Gingrich and Romney has become evident over the weeks, even as Romney says he holds no grudges against his rival though he revealed to reporters on his way to New Hampshire that he spoke Tuesday night with all his GOP rivals except Gingrich.

On Wednesday, he added that the former Massachusetts governor would bend to the will of the establishment rather than effecting change.

On Wednesday, Romney also rejected Gingrich's characterizations and suggested Gingrich is in no better position to fix Washington than he is as a "private sector" leader.

"I understand the speaker is plenty disappointed and I appreciate that," Romney said. "I think to fix Washington will take someone to come in from outside of Washington and we got a lot of politicians who would like to have the job of leading the country. I think it's time to have somebody who spent their life in the private sector leading Washington and getting America back on track."

As for Santorum, whom Romney bested in Iowa by just 8 votes out of more than 122,000 cast, he did "a heroic job" of visiting the entire state of Iowa, Romney said. During that time, however, Romney said he built a national campaign team and fundraising organization to serve him for the long haul.

In that team is Sen. John McCain, the 2008 Republican presidential nominee who campaigned for Santorum in 2006 but endorsed Romney on Wednesday.

"I'm really here for one reason and one reason only and that is to make sure that we make Mitt Romney the next President of the United States of America and New Hampshire is the state that will catapult him on to victory in a very short period of time. That's why I'm here," he said.

With the dynamics in flux, another wrench in any strategy to combine forces against Romney is Ron Paul, the fiercely libertarian Texas lawmaker who came in third in Iowa and said his goal is to appeal to independent voters of New Hampshire -- a larger segment of the vote than both Republicans or Democrats in the state.

Instead of targeting Romney, Paul on Wednesday told Fox News that Gingrich needs to "read the Constitution so he can find out what we're supposed to be."

Targeting Gingrich after the former speaker said his foreign policy views are "stunningly dangerous for the survival of the United States," Paul responded that the U.S. is "not supposed to be the policemen of the world."

"We're not supposed to start preemptive war and go in and occupy countries. Why don't we look to George Bush's advice? He ran in 2000 and won by saying we should have a humble foreign policy ... we shouldn't be in nation-building. So he's taken on George Bush, he's taken on the founders of this country. He's taken on (non-interventionist late Sen.) Robert Taft. He's taken on President Eisenhower, who warned is about bankrupting this country and kowtowing to the military-industrial complex."

While the top four in Iowa pick up another contender in New Hampshire -- Huntsman, the former Utah governor who sat out Iowa -- they did lose Bachman as a rival. The Minnesota congresswoman suspended her campaign Wednesday after a weak showing in Iowa.

Also perhaps not a factor in New Hampshire is Rick Perry, who on Tuesday night announced he would return to Texas to reassess his campaign, but Wednesday morning tweeted a photo of himself with the message, "Here we come South Carolina!!!"

A source with Perry's campaign told Fox News the former Texas governor is taking two days off but will attend debates in New Hampshire and start a "full-court press" in South Carolina on Sunday afternoon, before Tuesday's primary in the Granite State.

Perry's decision to stay in the race but detour to South Carolina, did not surprise state GOP Chair Chad Connelly, who said Perry could plow through to the Palmetto State.

"The reception has been really good for Governor Perry. I'd say he's been here six to eight times since he's got in the race in early August. He did a kick-off event here in South Carolina, of course, and he's been really well received," Connelly told Fox News Radio.