Polarization in American Politics

It's long been a pattern to "divide and conquer" the American voting public by playing up fears of each other. See Rick Perlstein's Nixonland for an account of how the Republican "Southern Strategy" consisted almost entirely of divisive tactics...

...and Karl Rove (whose beloved stepfather was gay, and who put gay marriage initiatives on the ballot in 11 swing states in a recent presidential rate) has made slicing and dicing the electorate into a fine art.

And here is what the result looks like. (Graphs!)