Everyone knows that the suburbs are a central battleground of the 2012 campaign.

But the “suburbs” is a very broad description that takes in areas that have very little in common aside from some basic geographic proximity to a major metropolitan area. Alexandria, Virginia and Purcellville, Virginia — for example — have very little in common other than they are both in the proximity of the D.C. metro area.

Thanks to the data and graphics gurus at the Washington Post — Ted Mellnik we are looking at you — we now can refine what exactly we mean when we talk about the the swing suburbs.

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. Need examples of mature suburbs? Loudoun County (Va.), Pima County (Ariz.), and Kane County (Ill.) all qualify.

In 2004, President George W. Bush bested Massachusetts Sen. John Kerry in the mature suburbs, which cast a total of 21.4 million votes, by nine points. Four years later, President Obama beat Arizona Sen. John McCain (Ariz.) in the mature suburbs 50 percent to 49 percent — winning two million votes more than Kerry in that key area.

Obama likely won’t win the mature suburbs in 2012 but he can’t afford to lose them by a double-digit large margin either.

The graphic below not only details the presidential candidates’ performance in the mature suburbs but also looks at how the 573 counties in the top 100 metro areas voted in 2004 and 2008. (Click here for a larger map.)

(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.)