On Fox News’ “Hannity,” frontrunner calls Santorum robo-call a “deceptive and a dirty trick.”

Romney: “It’s a new low in this campaign.”

Santo fires right back: “It’s interesting that he criticize me for attracting Democrats because one of the things that Gov. Romney, his people say is, ‘Oh, he can’t attract Democrats.’ Well, guess what? We’ll wait and see.”

Watch Mitt Romney’s “new low” remark below.

Watch Santorum’s response below.