The answer is probably “yes,” not because Specter will become an environmental champion but because his votes will shift at the margin. If you look at the LCV scores (here), Specter is below 50% this year and for his lifetime average. Part of that may be Pennsylvania — Bob Casey is only at 60%, which is well below the scores for Maine’s two Republican Senators. (If you look at the map, environmental voting scores are highest for states that border either Canada or the Pacific Ocean.) But Specter will now have to worry about facing opposition in a Democratic primary rather than a Republican one, so he may shift in Casey’s direction on environmental issues. Consequently, the future may look more like 2007, when Specter’s score was 60%, just at Casey’s average.
Specter is unlikely to support a fillibuster of legislation supported by the President and the Senate leadership. There’s also the psychological impact of the switch on the political dynamics, and the fact that until there’s a new agreement between the parties, the Republicans won’t be able to replace him on committees. The latter point is significant because he sits on Environment and Public works.
Overall, a good day for Greens.