Sen. Arlen Specter was a source of great angst to Republicans. But since switching parties he’s voted with them on two big issues — the budget and cram-down mortgages. In neither case was Specter the deciding vote. Nevertheless, he gives cover, or applies pressure depending on your point of view, to other moderate or conservative Democrats to flex their independent muscles. And, of course, he helps Republicans make the case that opposition to the president’s liberal agenda is not simply a partisan affair.

I’m sure the Democrats are happy to have Specter. But maybe a little less happy after these two votes. If they think they have a reliable supporter of the president’s agenda they may want to reconsider. And if they can predict where he’ll wind up on any given issue they are better mind-readers than their Republican colleagues.