I’m glad Sestak beat Specter in Pennsylvania. I have a great deal of respect for people who have left the Republican Party because it’s been taken over by lunatics, but Specter’s Shawkshank Redemption wasn’t very impressive.
On the other hand, I certainly appreciated having that sixtieth vote for the Access to Care act, and if Specter hadn’t thought that his party switch would save his political skin he wouldn’t have crossed the aisle. So if, the day before Specter switched parties, I’d been told that he would do so only if I and people like me promised to support him, I would happily have made that deal. No doubt the White House had to make that deal explicitly, and I don’t blame them for living up to the commitment.
Since there was no way of binding Democratic activists to such a deal, they went with the better candidate, and Specter is left without the promised reward of his apostasy. In the jargon of game theory, we faced a dynamic inconsistency: the strategy “promise Specter support” wasn’t subgame-perfect, since once he’d defected and couldn’t un-defect it was advantageous to dump him.
On balance, the disadvantage this situation causes for party-switchers is probably a feature, not a bug.