In states where Democrats won three of the past four elections, imports consist of as much as 60% of the market, while Republican strongholds favor domestics by up to 74%. The paradigm changes slightly in traditionally Democrat states that also produce a lot of cars and trucks. States like Wisconsin and Michigan still prefer domestic products. The three states that have been split over the past four elections also prefer domestic vehicles.
The exact reason for the phenomenon isn't clear, but a quick view of the political map shows that traditional Democrat strongholds are on the east and west coast, where imports are preferred. The center of the country traditionally favors Republicans, especially in the South. That's pickup truck country, and Ford, GM and Chrysler dominate the segment.
[Source: Washington Times | Image: Infovis.net]