There are, of course, the crazy MAGAs and the pardoned J6 army that would do Dump's bidding, including physically attacking Rs that go against his wishes. And Dump's promise to primary anyone who doesn't support the fascist agenda.
And then we see the Town Halls arranged by the Rs where local voters vociferously object to Dump's policies.
So which side are the Rs more afraid of?
And yes, Republican leadership could stand up. But Johnson certainly won't. He's a Christo-fascist nutter. John Thune? Unlikely.
I think some Republicans would defy Vance and insist of having their own way about some things. But the Republicans are terrified of their constituents.