Former House Speaker Newt Gingrich insisted on Tuesday that that fellow candidate Mitt Romney was a "liar," but could support him over Barack Obama if the former Massachusetts governor became the eventual Republican nominee.

At a Monday campaign event, Gingrich, who is running very few ads because of sluggish fundraising, had complained about Romney refusing to speak out against attack ads being aired by a pro-Romney Super PAC.

"Here is my simple tag line: Somebody who will lie to you to get to be president will lie to you when they are president," Gingrich told suporters.

In an interview Tuesday morning, CBS correspondent Norah O'Donnell asked Gingrich if he was calling Romney a "liar."

"Yes," Gingrich replied.

"You're calling Mitt Romney a liar?" O'Donnell pressed. "Why are you saying he is a liar?"

"Because 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."

After explaining that Gingrich had just called Romney a "flat-out liar," CBS host Bob Schieffer wanted to know if Gingrich could support Romney if he eventually won the GOP nomination.

"Sure," Gingrich said without hesitation. "I would support a Republican candidate against Barack Obama because I think Barack Obama is tearing the country apart."

"You're saying Mitt Romney would be a liar as president," O'Donnell pointed out.

"Yes," Gingrich agreed. "But less destructive than Barack Obama."

But there are some Republicans that even Gingrich would have trouble supporting over the current Democratic president.

In an interview with CNN last week, the Georgia Republican said that he could not vote for GOP hopeful Ron Paul.

Watch this video from CBS's The Early Show, broadcast Jan. 3, 2011.