Santorum still has a good chance at re-election. Remember that Planned Parenthood and NARAL have an absolute stranglehold on the Democratic Party and will do whatever they can to stop Casey from being nominated.
The pro-abort groups have been scared that the national Democratic Party is going to moderate its position on abortion, so I imagine they'll hit Casey hard and either beat him or wound him badly for the general. I believe part of the reason Casey lost the primary to Rendell was also because he was a lousy campaigner (the same cannot be said of Santorum).
We should hit Casey on the issue of judicial nominations. His pro-life views won't matter anything if he votes to block the president's judicial nominations. It's the silver bullet, I say.