And it has not happened long before Trump? I thought it had.
Now, of course, to the extent Trump makes it even more associated with the Republican party, it is a great gift for the Dems. Remember, US has FPTP a two-party system. Getting 40% of the vote is not enough to win elections. Both parties have to be grand coalitions, which means radicalism - in any dimension - is damaging. Limiting partisan base to just whites and desperately losing cities has already been a problem for the Republicans. The more openly anti-migrant speech will force minorities and urbanites even further into the Dem column.
I don't think it is as simple as FPTP determining it, although that is an important factor.
The way that American politics worked ever since Nixon's southern strategy through Obama was that Republicans would deliberately try to be as racist as possible and to receive as few votes as possible from blacks. The idea was that it was better to get
fewer votes from blacks, because then all of the white racists would flock to you. And that is exactly how it worked. That yielded the Nixon/Reagan landslides, and more or less worked to keep Republicans competitive in Presidential elections up until 2008. And it still works in midterms, when turnout is lower.
The problem with that strategy was that it eventually backfired. The problem is that education increased among white voters, and so the share of white racists dropped. At the same time, the minority population started to go up, and so did minority voter turnout.
But the southern strategy was premised on there being only one minority group (blacks), and upon there being enough white racists so that whichever party the white racists voted for (Republicans) would beat whichever party the African Americans voted for (Democrats). If the only minority group were blacks, then that would still even work. But the problem for the GOP is that then we started to have immigration from non-black minorities (chiefly Hispanics). And the problem is, you can't really be racist against ONLY blacks but not against other minorities, like Hispanics.
So what happened in 2008 is that those two trends of increasing minority vote share and increasing education among whites hit a critical point. White racists (plus business support and money) was no longer enough to overpower the combination of non-racist white liberals and minorities.
So the point is - this strategy did work in FPTP, it's just that it doesn't work any more.
Now, where Trump comes in on this is as follows. He is basically trying to do the same thing to Hispanics that Nixon did for blacks. Turn them into a monolithically Democratic voting group, in order to raise perception of racial threat among whites. If the only minority group were Hispanics, that would probably work. The problem is that there are also blacks, and they are solidly Democratic thanks to Nixon.
Anyway, the final conclusion from all of this is that it can work in FPTP systems, under some conditions. However, it won't work under the current conditions. The only way it could possibly work would be if you could somehow separate racism from anti-immigrant sentiment. That way, you could attract blacks into the Republican party on an anti-immigrant platform. That would be a large reversal from current voting trends, but that is the only way that this strategy is really viable, even in theory.
Absent that, the only path forward for the GOP is to stop being racist, and win over minority voters. The problem with that, though, is that even if you could get all the racists to stop caring about racism, then voting would become only about economic issues. And then the political coalitions would become 1 party representing the rich vs one party representing the poor. You would be back to New Deal coalition type politics, and that would be a disaster for the party of the rich (Republicans).
So to prevent that from happening for as long as possible, business interests are trying to foment as much racism as possible.
