“The overwhelming majority of U.S. counties are Republican; however, counties carried by Democrats are generally more densely populated. The county-by-county map, therefore, visually overstates the Republican share of the vote, because the Democratic votes are concentrated in fewer counties that cover a smaller land mass.” (Media Matters)

I would add the obvious fact that a region will show red whether the vote in favor of Bush was 70-30% or 51-49%. The ‘sea of red’ out there in the heartland is really a sea of purple, as boing boing pointed out. [Oh, how I wish I lived in a land of multiple political parties, coalition government, proportional representation and instant runoff voting…]