Isarithmic History of the Two-Party Vote.

David Sparks, a PhD candidate in political science at Duke University, has produced a fascinating video that details the shifting two-party vote over the last century, in isarithmic form. As he explains, isarithmic maps "are essentially topographic or contour maps, wherein a third variable is represented in two dimensions by color, or by contour lines, indicating gradations." The results vividly illustrate well-known -- but key -- developments in presidential politics since 1920:

A few things; as Sparks observes, the maps for 1924 and 2004 are nearly inverted, showing the South's transition from solidly Democratic to solidly Republican. What's more, we can clearly see the partisan lines shift from east/west (and to a lesser extent, north/south), to heartland/coasts, reflecting the collapse of New Deal liberalism and the 30-year dominance of movement conservatism. For now, the lines seem stable, but change is inevitable. I'll let Sparks have the last word: This video is a reminder that what constitutes "politics as usual" is always in flux, shifting sometimes abruptly. The landscape of American politics is constantly evolving, as members of the two great parties battle for electoral supremacy.

-- Jamelle Bouie

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