Romney plays it safe as GOP frontrunner

Mitt Romney's rivals took aim at him in Monday's South Carolina debate, but the GOP frontrunner largely played it safe, seeking to avoid missteps that could cost him before Saturday's primary.

Romney holds a commanding 23-point lead over the rest of the Republican field, according to a new national Gallup poll. But as he looks to protect his lead, he may run the risk of allowing his competitors get back in race, notes Jan Crawford.

That's what they tried to do Monday night.

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Gingrich hit Romney hard over negative ads run by super PACs supporting him, chiding the former Massachusetts governor to "exercise some leadership on his former staff and his major donors to take falsehoods off the air."

But Romney answered back, criticizing a Gingrich-aligned super PAC for putting out an attack ad that is "probably the biggest hoax since Bigfoot."

Rick Santorum set the tone early, aggressively challenging Romney on his gubernatorial record, and then taking on both Romney and Gingrich over reforming Social Security.

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"I want to make a point about Newt and his plans because they are not bold. And they're not in the case of Gov. Romney," he said. "First, we have to get our fiscal house in order, balance the budget and then create the opportunity that Newt wants. But the idea of doing that now is fiscal insanity."

At left, watch more Jan Crawford analysis on how attack ads are shaping the GOP primary race and what impact they might have in the general election.

Gingrich and Santorum are slugging it out to be the Romney alternative, but Texas Gov. Rick Perry also had a good moment - a reminder of why so many months ago many thought he could beat Romney - when he talked about getting America back to work.

"That's what I've done for 11 years as the governor of the 13th largest economy in the world. A million jobs have been created in our state."

But it was Texas Congressman Ron Paul who refused to back down-standing by his principles and defending some of his negative attack.

"There was one ad that we used against Sen. Santorum and I ... had only one problem: I couldn't get in all the things I wanted to say in one minute."

Watch Crawford's full report above.