To those who want to see the GOP expand and not contract, this should come as unwelcome news.
UPDATE: A predictable barrage of who-needs-him purism begins.
UPDATE2: Quiz question: What 1996 Republican candidate quoted Barry Goldwater's credo of keeping government "out of our pockets, off our backs and out of our bedrooms"? I'm not saying the candidate in question admirably lived up to that credo, but (memo to Matt Welch) Specter's departure isn't entirely a good thing if you'd like to see a GOP with more libertarian instincts.
UPDATE3: David Frum sums it up well: "Let’s take this moment to nail some colors to the mast. I submit it is better for conservatives to have 60% sway within a majority party than to have 100% control of a minority party. And until and unless there is an honored place made in the Republican party for people who think like Arlen Specter, we will remain a minority party."
UPDATE4: "RED TIL I'M DEAD BABY!!!"
UPDATE5: Specter offers a useful reminder of his opportunistic schmuckiness.