Electoral Map by Partisanship, County, Population Density -- by Chris Howard. Good stuff at the link, including high-res version. Red/blue maps exaggerate geographically-arge but population-light areas. Mapping at county level, 100 votes per dot, this colorization is a clearer portrait of the very mixed US political landscape. Population density is much more clear - try scanning westward from the East Coast, or see the distribution of voters in Florida, shown in a closeup).