Appearing in the journal Statistics and Public Policy:

The familiar U.S. electoral map — with the Democrats winning in the Northeast, upper Midwest, and West Coast, and the Republicans dominating in the south and center of the country — is recent. In the past few elections, rich states have gone for the Democrats and poor states have voted Republican, but 30 years ago there was no such pattern, and 100 years ago things looked completely different. . . .

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We are so used to the idea of cosmopolitan liberal Democrats and rural conservative Republicans that the 1896 pattern can come as a shock. What happened?

Was 1896 an aberration? No,

Were the rich and poor states in 1896 different than in 2000? No.

Have the parties changed what they stand for? On the general left-right economic dimension, not so much.

Have voters changed their priorities? Not so much.

Urban-rural divides: Vary by states.

The short story is that it’s a long story. We have a bunch of graphs.

We are used to our current political divides, but in many ways the political alignment of 1896 also makes economic sense, with the richer northeastern states supporting more conservative economic policies. Even in a world in which parties have static positions on issues, there is no obvious way that liberal New Yorkers, say, should vote: should they follow the 1896 pattern and support business-friendly policies that favor local industries, or should they vote as they do now and support higher taxes, which ultimately redistribute money to faraway states with more conservative values? A similar conundrum befalls a conservative Mississippian or Kansan in the other direction. In that sense, it perhaps is plausible that, although economic issues have been and remain most important in any particular election, social issues can be the determining factor that can, over a century, reverse the electoral map.