White Nationalism

White nationalism has been a pillar of Republican politics since at least Nixon (and probably Goldwater). The Wikipedia article called Southern Strategy gives a nice overview. One reason many folks moved from being Democrats (who used to be the party of the blue collar) to being Republicans is that Democrats, whatever their faults may be (and there are many), started to care about social justice. This means, in particular, taking social position from those that had held it (White Straight people, mainly men) and attempting to give it to ill-served minorities (African-Americans, LGBTQ, Women, etc). This is one of reasons for the rise in Trumpism. It is a backlash in response to the loss in social status.

One of the things that is interesting about our current society is that if you talk to actual brown people, you find that they are quite frequently conservative. This is perhaps not surprising. But the Republican party cannot be seen to be taking advantage of this. Perhaps one data point will help: Almost all of those 'terrible' people coming across the southern border are Catholic. Not known as a tremendously liberal religion.