(updated below - Update II)
I just contributed my thoughts on Arlen Specter's party switch to the New York Times' "Room for Debate" segment, so I'll post the link to that once that is available (see Update II), but for the moment -- and since this, presumably, is what many people want to discuss -- I'll note a few brief points:
(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.
(2) Democrats will understandably celebrate today’s announcement, but beyond the questions of raw political power, it is mystifying why they would want to build their majority by embracing politicians who reject most of their ostensible views.
Reports today suggest that Democratic officials promised Specter that the party establishment would support him, rather than a real Democrat, in a primary. If true, few events more vividly illustrate the complete lack of core beliefs of Democratic leaders, as well as the rapidly diminishing differences between the parties. Why would Democrats want a full-blooded Republican representing them in the blue state of Pennsylvania? Specter is highly likely to reprise the Joe Lieberman role for Democrats: a “Democrat” who leads the way in criticizing and blocking Democratic initiatives, forcing the party still further towards Republican policies.
(3) Arlen Specter is one of the worst, most soul-less, most belief-free individuals in politics. The moment most vividly illustrating what Specter is: prior to the vote on the Military Commissions Act of 2006, he went to the floor of the Senate and said what the bill "seeks to do is set back basic rights by some 900 years" and is "patently unconstitutional on its face." He then proceeded to vote YES on the bill's passage.
(4) Today is the best day to watch Fox News since the election -- mass grieving flavored by impotent bitterness.
UPDATE: In his Press Conference, Specter just reiterated that he opposes the nomination of one of Obama's few truly excellent nominees: Dawn Johnsen as OLC Chief. What a great Democrat Specter will be. Specter also just detailed how key Democratic officials promised to support him and raise money for him in the 2010 election if he switched, so now Democrats -- Harry Reid and the rest -- are committed to keeping him in power for another 8 years, committed to keeping the Pennsylvania Senate seat in the hands of Arlen Specter.
Specter is also complaining incessently about the fact that Lieberman lost his primary and Specter only won his 2004 primary by 1%. This apparently demonstrates all sorts of bad things about our political process. They really do believe that they are divinely entitled to keep their seats forever, and anything which threatens that is intrinsically illegitimate and wrong.
UPDATE II: The New York Times discussion on Specter to which I contributed is now available here.