What’s it all about, Arlen?

Pennsylvania Senator Arlen Specter, one of the three Republicans who compromised on Obama’s stimulus bill, has decided that he’s no longer a Republican. When Minnesota finally gets Al Franken seated, Specter will be the 60th Democrat, giving the party a theoretical filibuster-proof majority.

“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’s statement reads.

Translated from spineless politician-ese, that means “I was polling far behind in my projected primary battle, and Democrats in PA like me much better than Republicans do, so I’ll be more likely to get reelected with a D next to my name.”

Fabricio Rodriguez of Jobs With Justice in Philadelphia says, “Senator Specter is a curious type of politician. Rather than winning elections by aligning a plurality of devoted supporters, he prefers to strategically divide a growing majority of enemies.”

Apparently, the Democrats promised Specter not only a primary he was more likely to win—Specter is quite popular in Pennsylvania and raised nearly $20 million for his last reelection in 2004—but no opponent in that primary, though Joe Sestak, representative from Pennsylvania’s 7th District, won’t commit to not running.

Pennsylvania has a strong Democratic machine, a popular Democratic governor, and it can be hell trying to go up against the party establishment if they’re pledged to Specter. But as Sestak noted, it remains to be seen whether Specter will actually hold up his end of the bargain. Harry Reid is dumber than even I think he is, if he took Specter in and gave him sweetheart deals on committee posts without extracting some promises for support on key bills in return.

One of those key bills, as I noted before, is the Employee Free Choice Act. Specter reiterated his opposition to the act as written, but a few cracks may be showing in that decision. The AFL-CIO released a statement saying that they looked forward to “continuing an open and honest debate with Senator Specter.” And Politico reported that Teamsters President James Hoffa met with Specter on Monday morning to discuss EFCA.

Specter knows that union support is key in Pennsylvania—in 2004, he out-fundraised his Democratic opponent among labor interests by more than double, $341,000 to $141,000. If he doesn’t support EFCA or a compromise labor reform bill, he could find it very hard to keep up those fundraising numbers in a state where 16% of the workforce (847,000 people) is unionized—not to mention the numbers of ground organizers that come straight from union ranks to get out the vote come election time. Sestak or another progressive could easily pick up that union support if Specter doesn’t work with the unions on EFCA.

Even if Specter does manage to keep the support of the Democratic machine, it’s not unheard of to take on that machine. Michael Nutter, for example, managed to become mayor of Philadelphia against creatures of the machine like Representative Bob Brady. Progressives, instead of whining, should take a minute to see what we actually get out of Specter, and then organize.

After all, Bob Casey, Pennsylvania’s other senator, is not the progressive we’d like to see, either. He was an early endorser of Barack Obama against Hillary Clinton, but he is anti-choice and socially conservative, while Specter is pro-choice, supports affirmative action, and voted against CAFTA.

Lincoln Chafee, another centrist Republican who lost his seat after facing a primary challenge from the right, said, “It’s a numbers game, and the Democrats just got one more. [Specter] toed the party line a number of times and he doesn’t have to do that anymore. Now he can toe the Democrats’ line.”

Specter’s conversion to the Democratic party doesn’t make him any less of a fiscal conservative, deficit hawk, or “centrist.” He won’t be any more of a reliable vote on progressive issues than he ever was.

However, this is a tremendous, symbolic move. While the Republicans are struggling to rebrand themselves, consolidating their “message” as one of opposition to taxes—any taxes—support for torture, and knee-jerk anti-Obama blathering, one more member of the party stood up and said “This isn’t me.” Yes, he did it out of self-interest, but he made a very big, very visible gesture showing that the center is now firmly the domain of the Democrats. This is good news for the party.