You can draw a pretty clear line in the sand from when Specter went from sorta, kinda Democrat to OMG totally! Democrat, and it coincides with the date that Sestak announced his challenge.
The real question is how Specter will behave if and when he wins the primary challenge, and the pressure from the left is off. This is especially so now that some polling shows Republican Pat Toomey, who forced Specter from the GOP in the first place, competitive against him in the general election.
Indeed, Specter appears to be just as capable of reacting to pressure from his right as to his left. In reviewing Specter’s votes, I noticed that there was also something of a breaking point while he was still a Republican. In the first part of the year, after Barack Obama had carried his state by 10 points last November, he was voting with Democrats quite often, including on key measures like the stimulus package. But once the primary pressure from Toomey had begun to heat up — as emphasized by a shocking March 25th Quinnipiac poll that put Specter 14 points behind his Republican rival — he had become quite conservative, voting with Democrats only 16 percent of the time in his final month or so as a Republican.
There’s no doubt that Specter is the consummate political survivor, doing and saying whatever is necessary to live to fight another day. There’s no principle he won’t compromise, no ideal he won’t toss aside, if it helps him achieve victory in the next election.
The thing to remember throughout this cycle is that this is likely to be Specter’s last election. If he wins reelection, he’ll be 86 when his next term is up. So how will he act when he no longer has electoral pressures to keep him loyal to the Democratic Party? The charts above have the likely answer — his Democratic loyalty scores will be somewhere between 58-69 percent. He became a solid Republican when threatened from the Right, and he’s now a solid Democrat when threatened from the left. But when all’s said and done, and he’s not feeling the pressure, he becomes a Lieberman-esque thorn on his party-of-the-moment’s side.
This is the decision Pennsylvania Democrats will have to make — do they want an unpricpled Lieberman-style hack who will support Democratic priorities a bit over half the time, or someone more dependable?