Once again, I find myself agreeing with Dick Morris:
By the time all the primaries have been held, after June 3, there is no doubt that Obama will lead by more than 100 elected delegates, and likely 150. From there, it will be an easy route to the nomination. The Democratic superdelegates aren't about to risk a massive and sanguinary civil war by taking the nomination away from the candidate who won more elected delegates. If they ever tried it, we'd see a repeat of the demonstrations that smashed the 1968 Chicago convention and ruined Hubert Humphrey's chances of victory. Clinton won Pennsylvania for two key reasons: Only Democrats could vote in the primary, and the Keystone State electorate is dominated by the elderly, who are staunchly for Clinton.
Hillary's only chance is for Obama to self-destruct and he's not going to do that. Theoretically, Al Gore could jump in as a compromise candidate and win a second vote at a brokered convention, but he doesn't have the guts to try that sort of maneuver, and the party leaders aren't willing to wait until the convention to settle on a nominee. That means Obama is the man. Hillary is just in the way, causing trouble or as Rush Limbaugh would say "Chaos". Perhaps, she's hoping she can do enough damage to Obama so that he would lose in the general election and give her another shot in four years. That's an incredible long shot, but it wouldn't surprise me if that's the Clintonian Plan B at this point.