Our 2012 Election Heat Map colors each state according to the percentage of red and blue book purchases, based on shipping address, that have been made on Amazon.com during the past 30 days. We take the top-selling political books on Amazon.com and categorize them as "red," "blue," or neutral. We classify books as red or blue if they have a political leaning made evident in book promotion material and/or customer classification, such as tags. We compute percentages, updated daily, for each state and the US by comparing the 250 best-selling blue books during the time period against the 250 best-selling red books during the same time period, including new book launches.
The country is practically colored all red, so there's not a ton to glean from the map. Although I wonder what it'd look like at the county or city level. They should do that. I also wonder what other trends can come from Amazon sales data. They should do that, too.