I could spend a few paragraphs detailing my view on Arlen Specter’s party-switch bombshell today, but Nate Silver summarizes it perfectly in one pithy sentence:

Why should the Democrats settle for a Liberdem when they can probably get Pennsylvanians to elect a mainline Democrat along the lines of Bob Casey?

Seems the Dems are calculating that Arlen Specter as an independent (which would probably have been plan B) is too formidable an opponent in their efforts to flip the seat, so if ya’ can’t beat ’em….

But as Glenn Greenwald aptly points out:

(1) The idea that Specter is a “liberal” Republican or even a “moderate” reflects how far to the Right both the GOP and our overall political spectrum has shifted.

Consider Specter’s most significant votes over the last eight years, ones cast in favor of such definitive right-wing measures as: the war on Iraq, the Military Commissions Act, Patriot Act renewal, confirmation of virtually every controversial Bush appointee, retroactive telecom immunity, warrantless eavesdropping expansions, and Bush tax cuts (several times). Time and again during the Bush era, Specter stood with Republicans on the most controversial and consequential issues.

Edit: As rkatclu (one of our frequent commenters) points out, The Corner at National Review has a different take:

RE: Arlen Specter [Mark Hemingway]

I read that he was switching parties, but I was disappointed to learn he’s still a Democrat.

With the GOP in freefall is this the right time for the Dems to be playing defense?