Joe Sestak continues to hold on to a lead that he has held for over an hour, though it is steadily diminishing. But savvy Democrats can’t be too happy. Right now CNN is reporting that with 44 percent of the vote counted, Sestak is holding on to a slim four-point lead. But once you realize that 60 percent of Philadelphia’s vote is already in and 90 percent of Pittsburgh’s votes are counted, that means the bulk of the ballots that are not yet tabulated come from the rest of the state. As James Carville once quipped, Pennsylvania can only be understood politically as Philadelphia and Pittsburgh with Alabama in between. Which means that Sestak’s lead may well be short-lived.