Wow. If Al Franken is seated, the Republicans ability to filibuster is weakened. However, Specter says he won't be an automatic 60th vote to end filibusters.
Steve Benen and others argue that the significance of Specter's action isn't the ability to block the filibuster, but the fact that it paints the GOP as the party of wackos. Specter's move certainly adds momentum to the Democratic Party, while giving Republicans more reason to push Norm Coleman to do everything he can to keep Franken out of the Senate. And so it goes..
Josh Marshall's "holy crap" is the right response.
Kos points out the downside to this.