The idea of America as politically polarized—that there is an unbridgeable divide between right and left, red and blue states—has become a cliché. What commentators miss, however, is that increasing polarization in recent decades has been closely accompanied by fundamental social and...

In many many places, the political parties and political contests seem to array themselves along a single dimension. If you look at their programs in detail it always turns out that it's much more complicated than that. But it would appear that in the minds of the voters they are literally...