I hear a lot of people say this on FR, but not out in the “real world.” They are looking for someone to beat Obama, preferably not Romney. They will move to Santorum. I cannot prove it either. But the invective against Santorum does not seem that widespread, except among the GOP-E and liberals.
My radar goes way up when someone who says that the Paul voters will go with Romney under any circumstances. Ever run into one? They are all Paul all the time. If he isn’t running, they aren’t voting.