Last night on the Fox News All-Star Panel, Charles Krauthammer made an interesting argument about Pennsylvania senator Bob Casey’s Obama endorsement:

I think he might be overestimating the effect a little bit. Clinton has done a pretty good job of positioning herself as the working-class-whites candidate, and while Casey is a major figure in the state, I’m not convinced he can turn the tide. Also, when neither of the candidates is pro-life, I’m not sure it matters that Casey is.

But then again, the policy disagreements between Clinton and Obama are minor, so image, endorsements, and “electability” become more important.