Tribalism

I'm not terribly sure that it isn't as prevalent on the left, just different associations.  I am quite sure that most of the GOP base doesn't actually care about (or even like) most of the actual GOP platform. I thought that GOP party officials actually understood that but I guess not.

People who vote for Democrats want democratic policies enacted: tax the rich, improve social security, get everyone helth care, curb pollution...  People who vote for Republicans mostly just don't like people who vote for Democrats.  Oddly, though, they do like a lot of Democratic positions: they like social security and medicare, they have no problem with taxing the hell out of rich people, most of them don't really even care about stopping the gays from marrying or women from having control of their bodies beyond the fact that gays and womenfolk are more liberal and "fuck the librulz."

I've wondered in the past whether the continued rightward movement of "centrist" Democrats like Clinton would eventually lead to some Republicans taking over the liberal positions left behind (confiscatory taxing of the rich, and more generous social security/medicare, jailing the heads of corporations who destroy communities/environments).  Trump actually kind of does this.  To be fair his positions on the issues aren't exactly clear, but it doesn't matter because he hates on the libturdz and the corporate GOP both and his supporters love him for it.