So here is a plot of the 2002 Democratic Primary for governor when Rendell and Casey were fighting it out compared to the results yesterday. Each bubble represents a county and the size of the bubble represents the overall size of Democratic party turnout yesterday.
What's it mean? Clearly the negative correlation proves the obvious that the Rendell voters in 2002 were much more likely to be the Barack votersin 2008. Yet the story I would say is in just how strong that correlation is (or isn't actually). Philadelphia in 2002 went 78.5% for Rendell while yesterda it was 65% for Barack. That difference probably outweighed the margins Clinton got in dozens of other counties. If Barack had received the same 78.5% yesterday it would have been almost 60K more votes which could have canceled out the Clinton margins in 36 other counties combined. and that is talking just about Philadelphia.
Most counties followed the pattern that Rendell support in 2002 mirrored Barack support in 2008. By my quick count, only 7 of 67 counties 'flipped' support in any way. 5 counties supported Rendell in 2002, but went for Clinton in 2008: Berks, Bucks, Lehigh, Montgomery, Northampton.... while 2 counties that supported Casey in 2002 went for Barack in 2008: Dauphin and Union.