Unlike the debate a night earlier, essentially a bitter battle for second place, the candidates directed most of their fire at Romney, who's expected to coast easily to victory in New Hampshire's first-in-the-nation primary but will face far more socially conservative voters in South Carolina in two weeks.
"Can we drop a bit of the pious baloney?" Newt Gingrich said, his temper finally flaring as he listened to Romney extol his private enterprise experience while dismissing career politicians during NBC's "Meet The Press" debate.
The former speaker of the House of Representatives, who blames Romney for his falling fortunes in the race to take on President Barack Obama in November, said his rival has spent years either in office or trying to win elected office.
Romney and Gingrich finally had it out over the attack ads that have so peeved Gingrich. Romney defended the ads dissecting the one-time speaker's record as accurate, while saying Gingrich's branding of him as a liar regarding the spots was "over the top."
"You think my rhetoric was over the top, but your ads were totally reasonable?" Gingrich asked.
After insisting he hadn't seen the attack ads, Romney proceeded to detail their content. Gingrich did indeed get pushed out of his job as speaker by his Republican colleagues, Romney said, he did call for a climate change bill alongside top Democrat Nancy Pelosi, and he did malign Republican Paul Ryan's budget reduction plans as "right-wing social engineering."
Gingrich then issued what seemed a veiled threat. The former speaker's campaign is planning soon to run a 30-minute counter-attack against Romney, detailing his past work at private investment firm Bain Capital.
"I'm taking his advice," Gingrich said, referring to Mr. Romney. "It takes broad shoulders to run."
Throughout the debate, Romney also defended not only his private enterprise experience, but his stewardship of the state of Massachusetts when he served as governor there for four years. He also took aim at his favoured target, Obama.
"We've got to nominate a leader if we're going to replace someone who's not a leader," he said.
Santorum, who came within a few votes of beating Romney in the recent Iowa caucuses, asked why Romney didn't run for re-election in Massachusetts in 2007 if he was so proud of his record in the state.
Jon Huntsman, meantime, seemed the crowd favourite as he rapped Romney's knuckles for questioning Saturday night why he took a job from Obama to serve as ambassador to China.
"I was criticized last night by Gov. Romney for putting my country first," said Huntsman. "He criticized me while he was out raising money. I want to be very clear. I will always put my country first."
Romney retorted: "I just think it's most likely that the person who should represent our party against President Obama is not someone who called him a remarkable leader."
Huntsman, who has spent more time in New Hampshire than any other candidate in an effort to woo the state's primary voters, was cheered when he replied: "This country is divided because of statements like that."
Later in the debate, Huntsman was applauded again when he pointed to his fellow candidates and said "everybody's got something nasty to say" about various issues, including same-sex marriage.
Americans are distrustful of politicians and tired of divisive politics, he added.
"They want a leader who's going to unify," Huntsman said, adding he intended to attack "that trust deficit" just as surely as he'd attack the federal deficit if elected president.
Ron Paul's campaign, indeed, was sending out emails attacking Huntsman throughout the debate, suggesting Paul, in second place in the polls in New Hampshire, is nervous about the former Utah governor. According to a new Suffolk University survey, Huntsman's in a third-place tie with Gingrich and Rick Santorum.
South Carolina holds its own primary Jan. 21. Primary voters there are far more socially conservative than those in New Hampshire, and yet Romney, long distrusted there as a moderate, is ahead in the polls in the so-called Palmetto State.
The candidates faced questions about same-sex marriage Sunday, an issue that likely had voters in South Carolina sitting up and taking notice.
Santorum, a staunch social conservative, once compared homosexuality to bestiality.
The former Pennsylvania senator said he supports "equal rights" for gays, but opposes gay marriage. But he stressed that he is respectful of those who support gay rights.
"We may not agree. That's why we leave it open to the public," he said.
When asked how he'd respond if his son told him he was gay, Santorum replied: "I would love him as much as I did the second before he said it." Previously, Santorum has said he would encourage his son to suppress his sexual desires in such a scenario.
There were moments of levity at the debate, especially when Texas Gov. Rick Perry remembered the three federal agencies he's proposing to cut to reduce the country's massive national debt.
His failure to recall those agencies resulted in his infamous "oops" moment in an earlier debate that was thought to have delivered a near-fatal blow to his campaign.
"Let me answer the question that you asked earlier: what would be the three areas that you would make some reductions and people would feel some pain," Perry said to moderator David Gregory.
"And I'll tell you it would be those bureaucrats at the Departments of Commerce and Energy and Education.
Perry, beaming widely, held up three fingers in triumph as the crowd cheered, his opponents laughed and applauded and Santorum held up three fingers in solidarity.