A combined 60% of Republicans say Trump's endorsement either has no effect on their vote or makes them less likely to back Perdue (as opposed to 37% who say it makes them more likely to vote for the Trump-backed candidate). Clearly Trump's grip on the party isn’t what it used to be.
If you look at his most contested candidates and their share of the vote so far
Vance - 32%
Oz - 31%
Herbster - 30%
McGeachin - 32%
Perdue? -
It's roughly same 30-35% of the party that was unshakably loyal to him in the 2016 primaries. The other larger portion of the party likes him as president but isn't deferential to him in voting behavior. It is not at all the "cult of Trump" so many want to believe it is.