Very interesting new draft from Brian Amos and Michael McDonald up on SSRN:

Voters express varied levels of support for the parties’ candidates depending on where they live, be it in the South (Aldrich 1995; Carmines and Stimson 1989) or rural and urban sub-regions (Gimple and Karns 2006; McKee 2008). To investigate the importance of geography to vote choice among racial and ethnic groups, we develop a new national dataset of 2008 presidential election results within 166,260 precincts merged with census demographic data. We apply methods of ecological inference to these data to estimate voting patterns among racial and ethnic groups nationally, within the South and non-South sections, and among rural and urban areas within these sections. We find Southern White voters’ support for Obama to be less than Whites elsewhere, and that rural Whites similarly support Obama less than urban voters. These tendencies are compounded for rural Southern Whites, suggesting that these voters are the most distinctive. We explore these findings with respect to the continued need for voting rights protections in certain areas of the country where racially polarized voting is at its highest levels, and recommend that Congress adopt a measure of racially polarized voting in an updated coverage formula for Section 4(b) of the Voting Rights Act, recently struck down by the U.S. Supreme Court in Shelby County v Holder.