The author of a book on cults made that case to an interviewer on Vox.com a few days ago. The Vox interviewer, who noted that Trump uses the same mechanisms of communication as every other politician, seemed dubious, and with some reason.
Neither party to the interview really said this, but the principal reason the issue comes up is that the GOP as a whole has been willing to abandon some of its core beliefs just to satisfy his whim. Russia used to be an enemy; today, Putin is our ideological soul mate. The FBI and the CIA used to protect us; now, they’re the deep state. Kim Jong Un used to be a murderous dictator; now, he’s sort of a good guy. Free trade used to be a positive thing; today, we embrace tariffs. And so on.
I think the true test of the theory will come if Trump ever abandons his support of regressive tax cuts and embraces the economic ideas of “national conservatism.” Would the GOP establishment be willing to go that far? At this point, anything seems possible, but it’s doubtful we’ll ever find out, as Trump’s populism on domestic issues has always been restricted to his style, not his substance.