It is the battle of the PA heavyweights:
Casey, the son of a popular late governor, had said earlier this month he would not endorse before the April 22 primary out of concern for party unity. But he joined Obama at a boisterous rally kicking off a six-day bus trip through Pennsylvania, where current Gov. Ed Rendell has been campaigning hard for Clinton.Which machine will win.
At this stage, Obama doesn't need a win, just a narrow loss to keep the delegate lead.