The growing spatial polarization of presidential voting in the United States, 1992-2012: myth or reality?

There has been considerable debate regarding a hypothesis that the American electorate has become spatially more polarized over recent decades. Using a new method for measuring polarization, this paper evaluates that hypothesis regarding voting for the Democratic party's presidential candidates at six elections since 1992, at three separate spatial scales. The findings are unambiguous: polarization has increased substantially across the country's nine census divisions, across the 49 states within those divisions, and across the 3,077 counties within the states - with the most significant change at the finest of those three scales.