In a September debate, he promised to repudiate intra-Republican attacks and called his party's slate of candidates a "team."

In recent days, Newt Gingrich has been excoriating Mitt Romney in television ads and attacking his business background in language that President Obama would likely repeat in a general election.

"The most significant campaign news of the last few days was not the debates over the weekend, or even today's New Hampshire primary," Brendan Nyhan wrote. "Rather, it was the report that a super PAC backing Newt Gingrich will air millions of dollars in negative ads against Romney in South Carolina, the site of the next Republican primary after New Hampshire."

Amusingly, it wasn't so long ago that Gingrich got all sanctimonious about what he cast as a principled refusal to attack fellow candidates for the Republican primary. As he put it in September 2011:

JOHN HARRIS: Speaker Gingrich, it sounds like we have a genuine philosophical disagreement. In Massachusetts, a mandate, almost no uninsured--in Texas, a more limited approach, about a quarter uninsured. Who's got the better end of this argument?

GINGRICH: Well, I'm frankly not interested in your effort to get Republicans fighting each other. The fact is-- HARRIS: Speaker Gingrich, we've got--

GINGRICH: No, no we don't--

HARRIS: We've got a choice between the individual mandate or not. Anyway, go ahead.

GINGRICH: You'd have, you would like to puff this up into some giant thing. The fact is, every person up here understands Obamacare is a disaster. It is a disaster procedurally. It was rammed through after they lost Teddy Kennedy's seat in Massachusetts. It was written badly, it was never reconciled. It can't be implemented. It is killing this economy. And if this president had any concern for working Americans, he'd walk in Thursday night and ask us to repeal it because it's a monstrosity. Every person up here agrees with that. And let me just say-- since I still have a little time left, let me just say--

HARRIS: Sure.

GINGRICH: I for one, and I hope all of my friends up here, going to repudiate every effort of the news media to get Republicans to fight each other to protect Barack Obama who deserves to be defeated. And all of us are committed as a team, whoever the nominee is, we are all for defeating Barack Obama.

Then there's the statement the Gingrich campaign made last month: "Negative attacks on fellow Republicans will not create a single new job or help rebuild America... The Gingrich campaign has a different approach than some other Republican campaigns: Newt Gingrich has only one opponent -- Barack Obama."

Even in a race with Romney, Gingrich is as phony as they come.