The aftershocks are still rippling, and the analysis is just beginning, but the defection of Arlen Specter is certainly one of the most interesting political stories since the election in November.

Most critical to the Republicans is the potential for a filibuster-proof Senate (if Al Franken gets seated) for the first time since the late 1970s. Beyond the short-term, there is the future. Specifically the 2010 midterms, when Pennsylvania is sure to be one of the most closely-watched battlegrounds.

Specter will undoubtedly get support from the White House and the PA Democrats, which makes his path through their primaries look reasonably clear. He will face a young, up-and-coming Democrat by the name of Joe Torsella, who has long been considered a favorite of PA guv Ed Rendell. Rendell is also friendly with Specter though, which could lead to Torsella’s anticipated support from Harrisburg to evaporate.

But if Torsella can beat Specter, it likely gives the GOP candidate a better shot in the general election.

Now who exactly that GOP candidate is going to be isn’t as clear to me.

Obviously, Pat Toomey, who nearly defeated Specter the last time around in the Republican primary, is the clear favorite. But the very conservative Toomey is losing Specter as an arch-rival. This opens the door to any number of less conservative candidates, who are not quite as moderate as Specter, to take on Toomey in the primary. Rep. Jim Gerlach has been making noise about a run for governor, but given the drastically altered landscape, he could very easily run for Senate. Pat Meehan, a former DA, is another Republican who may be interested in a run for governor, but could switch gears.

And then there’s the big name: Tom Ridge.

Tom Ridge would bring massive name recognition and would instantly be someone who could win an increasingly blue Pennsylvania against a Democrat, even a Democrat named Arlen.

Ridge, while also a moderate, is likely to be far more loyal to the Republican caucus then Specter ever was as the senior Senator from the Keystone State. Local radio host Michael Smerconish floated Ridge’s name this morning on his show, and there are some out there calling for moderate Republicans to draft Ridge to take on Toomey in the primary.

Will it happen? Probably not. Ridge is making buckets of money in the private sector, and he may feel more than a bit unhappy with the party that passed him over as a VP candidate several times because he was “too moderate”. (I still personally think he was McCain’s first choice to be VP last year, per some sources I have)

But if Ridge were to run, I think he could beat Toomey and Specter, giving the GOP a much more reliably Republican vote out of PA.