Cillizza on "Mature Suburbs"

Chris Cillizza wrote his column in the Washington Post today on one of the battleground areas in the 2012 presidential election.  "The 'mature suburbs' are the 2012 battleground," can be summed up in this sentence:

It’s the “mature suburbs”, areas that are 75 percent to 95 percent urban, where the battle between President Obama and former Massachusetts governor Mitt Romney will really be waged.

In the map accompanying his article, you can see how many of the collar counties around Philadelphia are among the areas higlighted, but those aren't the only parts of the state in play.   Cillizza ends his article with this:

(Fascinating factoid: Of the six counties on the map that went from Democratic in 2004 to Republican in 2008, three of them were in southwestern Pennsylvania.)