Arlen Specter’s buddy seems to be in deepening re-election trouble according to a new Keystone Poll out this week(as Buzz reported; here’s the whole poll): the incumbent Republican now trails Democrat Bob Casey Jr. by a 44% to 37% margin in the 2006 Senate match-up. In the previous Keystone survey conducted in March, Casey led Santorum 44% to 43% — the son of the late popular governor may not be moving ahead, but the incumbent (whose “favorable” numbers aren’t) is falling behind. This one is going to be a doozie.