What's the best way for Mitt Romney to stop Rick Santorum?
For the answer, we went to someone who has done it before.
Democratic strategist Saul Shorr helped Bob Casey defeat then-Sen. Santorum, R-Pa., in a landslide in 2006. Santorum lost by 18 points.
But Shorr says that was a general election; in a Republican primary, Romney will have a much harder job.