The video: Newt Gingrich has repeatedly pledged to refrain from launching negative attacks on his opponents. But with the Iowa caucuses mere hours away, and his poll numbers plummeting, the GOP presidential hopeful's gloves are coming off. In an interview with CBS News correspondent Norah O'Donnell on The Early Show Tuesday morning, Gingrich took brutal aim at Mitt Romney. After reading Gingrich a previous quote in which the former House speaker had questioned his rival's integrity as it related to a Romney-aligned super-PAC, O'Donnell asked, "Are you calling Mitt Romney a liar?" Newt paused for only a beat before answering, "Yes." A rather flabbergasted O'Donnell repeated her question, and Newt responded again in the affirmative. (Watch the video below.) "This is a man whose staff created the PAC, his millionaire friends fund the PAC, he pretends he has nothing to do with the PAC — it's baloney," Gingrich said. "He's not telling the American people the truth." When pressed later on whether he'd support Romney in the general election, Gingrich replied, "Sure."

The reaction: Gingrich is right, says Steve Benen at Washington Monthly. Romney has been "lying uncontrollably" throughout the campaign. The only surprising aspect of this interview is that O'Donnell seemed so shocked by Newt's accusations. Too bad this attack is too late to help Gingrich in the caucuses, says Glynnis MacNicol at Business Insider. If anything, this may reflect poorly on Gingrich, says Jed Lewison at Daily Kos. He called Romney a liar, and then implausibly said he'd vote for him in the general election. "With endorsements like that, Romney doesn't need opponents." Watch for yourself: