There’s a lot of interesting stuff in this John Dickerson article on what last night’s results really mean, but this last paragraph is probably the one that needs to be most referenced:
The night showed just how limited Obama’s political power is. He said he’d work all-out for Specter, but he didn’t campaign for the senator in the final days. That may have been a wise reservation of his political capital (he’s already been ineffective in previous races), but it also demonstrated how much has changed since 2008, when Obama was talked about as a force that could remake the political landscape. Critz won by running away from Obama’s signature achievement, and Lincoln, whom he supported, was forced into a runoff. For a president who is still far more popular than the Democratic Congress he aims to help, yet who is unable to translate much of that popularity to do so, this condition may be best described as limbo.