The first reaction many people may have when looking at a standard red/blue map of county-level election results is often "Holy crap, look at all that red!" While that huge red bulls-eye in the nation's middle is easily explained away—trees and tumbleweeds don't vote; only people do—when it's presented without disclaimers, it can help reinforce the perception that this is a "center-right nation." One of the best ways around that is with a cartogram (a map that distorts boundaries to account for another variable, like population) ... but how do we express that in a way that still looks like the United States, and not a piece of purple roadkill?
Princeton's Robert Vanderbei put together a fantastic 3-d map in 2012... that visualizes the country with blue skyscrapers towering over pink plains, reflecting the heavy concentration of votes in urban areas. However, I wanted to try going in a different direction, with a flat map, but one where the color varies by intensity according to the change in the number of votes over the years.
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