I'm glad you made the point--which can't be stated enough--that assuming new citizens will be a monolithic voting bloc isn't just racist but, like you say, profoundly stupid. One might think conservatives might see new arrivals as potential new recruits, but of course that's not really the game.

One of the ironies of Republicans adopting replacement theory is that it's an implicit concession that their party is intellectually bankrupt and limited in its appeal: they're not saying, "Yay, more potential converts to Milton Friedman!" for example.