Pennsylvania Senator Arlen Specter’s announcement that he is switching from Republican to Democrat  follows a poll which showed him trailing former Congressman Pat Toomey in a Republican primary by a 51%-30% margin. In contrast, Specter’s numbers have been pretty positive among Democrats and Independents.

It’s worth noting that that Specter has not committed to voting for cloture on all issues, and specifically said he will not vote for cloture for the labor unions’ card check bill. This might whet the appetite of the unions to run someone against him in the Democratic primary. But in the meantime, once Al Franken is seated (assuming he is), the Democrats will have 60 votes in the Senate. Not all of them are certain for cloture on every issue; others besides Specter have indicated they will not vote to move forward to pass card check. But it puts Democrats in a position of greater strength than they had yesterday.