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 fi ndings 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 signifi cant change at the fi nest of those three scales.
W riting in 2005, Glaeser and Ward addressedwhat they termed five myths regarding American political geography, of which the second was "the two parties [Republican and Democrat] are more spatially polarized than in the past" (Glaeser and Ward 2005 , 5). They claimed that "the number of states that can be considered 'safe' for either party has not been rising over time" and, using the well-established dissimilarity index for measuring spatial segregation, demonstrated that "county-level evidence shows that segregation by party is not signifi cantly increasing"-although they did identify a "slight upward trend" over the four Three years later, in a much-discussed book ( The Big Sort ), Bishop and Cushing ( 2008 ) argued that electoral polarization had indeed been taking place over the preceding three decades, as a result of sorting processes consequent upon major volumes of inter-region, inter-state and inter-community migration. Abrams and Fiorina ( 2012 ) published a major critique of The Big Sort , challenging both the conclusion that polarization had occurred and the processes-selective migration-that Bishop and Cushing claimed were the cause of that geographical outcome. Looking only at the fi rst part of that challenge-whether or not spatial polarization had occurred-Abrams and Fiorina rightly criticized Bishop and Cushing for relying on two arbitrary end-dates (especially the fi rst) to establish a trend. They also questioned the use of the binary division of the country into "landslide" and "non-landslide" counties as the elements of the portrayal; other indices suggested to them that counties were becoming "increasingly politically heterogeneous, not increasingly homogeneous" (Abrams and Fiorina 2012 , 205