Weathermap History of the US Presidential Vote 

  David Sparks  has drawn up some  isarithmic maps  of the two-party presidential vote over the last 90 years. An isarithmic map is sometimes called a heat map, and you would most often see a rough version of them on your local weather report. David shows us the political weather over time: 

     

 As you can see, the votes have been smoothed over geographic space. David also has a  video  where he smooths across time, leading to very beautiful plots. You should also see the summary of how he made the plots. A good reminder of the death-by-1000-papercuts nature of data analysis: 

 
   Using a custom function and the interp function from  akima , I created a spatially smoothed image of interpolated partisanship at points other than the county centroids.
  This resulted in inferred votes over the Gulf of Mexico, the Atlantic and Pacific Oceans, the Great Lakes, Canada and Mexico -- so I had to clip any interpolated points outside of the U.S. border using the very handy pinpoly function from the  spatialkernel  package. 
 

 My only worry is that spatial geography might be the wrong dimension on which to smooth. With weather data, it makes obvious sense to smooth in space. A suburb of Chicago might have more in common with a suburb of Cleveland than it does to Chicago, even though it is much closer to Chicago. Thus, this type of smoothing might understate real, stark differences between local communities ( Clatyon Nall  has some work on how the interstate highway system has accelerated some of these divides). Basically, I think there is a political space that fails to quite match up to geographic space. (Exploring what that political space looks like and why it occurs would be an interesting research project, at least to me.) 

 You should really explore the rest of David's site. He has numerous awesome visualizations.