The gloves came off as each candidate criticized his political and professional track record on the eve of the state's primary election.
Former house speaker Newt Gingrich fired the first salvo, claiming Romney is not conservative enough to win a campaign against President Barack Obama.
"I think that a bold Reagan conservative with a very strong economic plan is a lot more likely to succeed in that campaign than a relatively timid Massachusetts moderate," Gingrich said.
Romney responded, saying New Hampshire voters should rely on their own memory of his record in neighboring Massachusetts.
"People have watched me over my term as governor and saw that I was a solid conservative and that I brought change to Massachusetts," Romney said.
Then, former Pennsylvania Sen. Rick Santorum joined the conservative tag team.
"If his record was so great as Governor of Massachusetts why didn't he run for re-election?" Santorum said. "I mean if you didn't want to even stand before the people of Massachusetts and run on your record, why didn't you? Why did you bail out?
Romney responded with, "Run again? That would be about me. I was trying to help get the state in the best shape as I possibly could."
During Saturday night's debate, Santorum, Gingrich and Texas Gov. Rick Perry misfired in their attempts to emerge as a conservative alternative to Romney, hoping to parlay that status into victory later this month in socially conservative South Carolina. On Sunday morning, not far from the debate scene, diners at Concord's Red Blazer restaurant watched over breakfast.
"I think its interesting for them to come out and attack each other a little bit," New Hampshire voter Robert Fishwick said. "I think that makes for a good debate."
Former Utah Gov. Jon Huntsman also lashed out at Romney, who has criticized Huntsman's service as the Obama administration's ambassador to China.
"This nation is divided because of attitudes like that," Hunstman said. "The American people are tired of the partisan division."
Romney did not let up.
"I think we serve our country first by standing for people who believe in conservative principles and doing everything in our power to promote an agenda that does not include President Obama's agenda," Romney said.