One potential Republican candidate is warning that people should mind their comments around Sarah Palin -- because the former Alaska Governor has a gun.

"What about that Sarah Palin. She's not ready to be president, is she?" David Letterman asked former Mass. Gov. Mitt Romney Tuesday night.

"She's terrific. She really is. She's terrific. She's got energy. She's got energy, passion," Romney said as the crowd moaned.

"By the way, you know, be careful what you say about her by the way," Romney warned.

"I've had my..." Letterman started.

Letterman was referring to controversy that started after he compared Palin to a "slutty flight attendant" and a joke he made about Palin's daughter's promiscuity.

The former Massachusetts Governor cautioned Letterman to steer clear of the Palin in the future. "She has a rifle, you know," he said.

Romney appeared on Letterman's show to promote his new book, "No Apology: The Case for American Greatness."

This video is from CBS' Late Night with David Letterman, broadcast March 2, 2010.

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