I guess the American political parties have shifted over historical time, but they haven't shifted much in the last 4 decades or so. And there are pretty reliab

I guess the American political parties have shifted over historical time, but they haven't shifted much in the last 4 decades or so. And there are pretty reliable ideological differences between democrats and republicans, across a wide variety of issues. Of course, you lose a lot of information with a binary classification, but the binary classification still tells you quite a bit in this case.