CONCORD, N.H. – Newt Gingrich told him to “drop some of the pious baloney.” Rick Santorum asked “why did you bail out” and not run for a second term as governor of Massachusetts.

Two days before the New Hampshire primary, front-runner Mitt Romney was under siege here in a presidential debate hosted by NBC and Facebook, which aired on Meet the Press.

The second debate in 10 hours was no sleepy Sunday morning affair. Moderator David Gregory stoked attacks on Romney from the first question, to Gingrich, the former Georgia congressman and U.S. House speaker, about whether Romney was electable.

Gingrich gave an abbreviated, and slightly toned down, version of his stump contrast of a “Reagan conservative” and a “relatively timid Massachusetts moderate.” He got feistier as the debate continued.

Romney responded to Santorum, the former Pennsylvania senator, questioning of why he did not seek a second term if his record as governor was so great by railing against career politicians: "Run again? That would be about me. I was trying to help get the state in best shape as I possibly could."

Making oblique reference to Santorum’s and Gingrich’s lucrative post-Congress careers, Romney attacked politicians who “go to Washington for 20 and 30 years who get elected and then when they lose office they stay there and make money as lobbyists or connecting to businesses, I think it stinks.”

Gingrich, after calling the response “pious baloney,” pointed out that Romney ran for Senate in 1994.

"Level with the American people,” he said. “You've been running at least since the 1990s."

Romney said his races were not a career but guided by what his father, former Michigan governor and onetime presidential hopeful George Romney, told him: “Mitt, never get involved in politics if you have to win an election to pay a mortgage. If you find yourself in a position when you can serve, why, you oughta have a responsibility to do so if you think you can make a difference."

Romney said he was proud of a tough race he ran against Democratic Massachusetts Sen. Edward M. Kennedy and “I was happy that he had to take a mortgage out on his house to ultimately defeat me.”

Gingrich and his allies have been steadily escalating his attacks on Romney – on the campaign trail and in advertising – since his poll numbers plummeted amid a negative advertising spree in Iowa, particularly by a Romney-connected Super PAC called “Restore Our Future.”

Super PACs, which can raise and spend unlimited money on behalf of candidates but not coordinate with them, have become a driving phenomenon of the Republican presidential race.

Gregory asked if Gingrich, who has vowed a positive campaign, was being consistent when a Super PAC of his own is putting out a film accusing Romney-owned Bain Capital of being a “predator” when it took over struggling companies and laid off workers.

Gingrich said he was and that he hopes the film is factual. But he noted the main Restore Our Future ad – about Gingrich’s “baggage” – earned “Four Pinocchios” from the Washington Post’s fact checker for distortion. Gingrich’s legal team is trying to get the ad taken off the air in South Carolina.

Romney took the question as an opportunity to recite the attacks in the ad: That Gingrich had to pay legal fees for an ethics investigation during his tenure, that he shot an ad with then-Speaker Nancy Pelosi on climate change.

Romney added, “If there was something related to abortion that they said that was wrong, I hope they pull it out.” The line he was referring to stated that as Speaker, Gingrich “supported taxpayer funding of some abortions.” It is a reference to Gingrich’s defense of the Hyde Amendment, which bans all taxpayer abortion subsidies except in cases of rape or incest. The Washington Post called the line a "sleazy mischaracterization."

“I’m glad finally, on this stage and weeks later, he’s said, ‘Gee, if they’re wrong, take them down,’” Gingrich replied.

Romney added that some of Gingrich’s criticisms on him were “over the top.” But Gingrich noted that Romney once said the anti-Gingrich ads are just part of rough-and-tumble politics.

“I’m taking his advice,” Gingrich said.