I wouldn't be too concerned about Specter. I think it would be unprecedented for a Senator from the same party as the President to oppose a Supreme Court nominee from a district court bench whose jurisdiction includes the state that the Senator represents.
I'd love to think that Alito's being from Specter's area is quite a bit of leverage. It usually is. I just hope and pray that as a consequence, Alito was one of the suggestions that Specter made during discussions with WH... I've heard nothing to suggest that to be true so far, though. That does not bode well, it seems - but still he is from that district... Here's hoping - because I really believe that Specter is THE most imortant now - not just for Alito, but for ANY USSC nominee to have an honest chance after the way Miers (who he supported) was treated.