A little while ago, my colleague Mike Crowley heard from sources that Arlen Specter is leaving the Republican Party. And I see now that the Washington Post is reporting it, as well. But the headline currently on the Post home page--"Democrats Get Filibuster-Proof Majority"--is bit overstated.
Yes, the Dems will have sixty votes in the Senate. But Colorado Nebraska Senator Ben Nelson isn't a reliable Democratic vote and, to a lesser extent, neither are moderate Dems like Indiana's Evan Bayh.
Still, this is a big deal. And the reason, I would argue, can be found in the statement Specter just released:
Since my election in 1980, as part of the Reagan Big Tent, the Republican Party has moved far to the right. Last year, more than 200,000 Republicans in Pennsylvania changed their registration to become Democrats. I now find my political philosophy more in line with Democrats than Republicans.
Specter is one of the better-known senators in America. If you follow politics even casually, you've seen or heard him on the news before. So it's going to register with you that a major Republican senator has decided his party has become too extreme for him. And if you're a Republican, you might wonder if it's become too extreme for you, as well.
Of course, polls show voters leaving the Republican Party already. And not just in Pennsylvania, as Specter noted. The real significance here may be less about political change to come and more about political change that has already happened.
Update: TPM's Eric Kleefeld has more analysis, complete with demographic trends.
--Jonathan Cohn