There used to be a time when Senate leaders would take the problem members of their party into the cloak room and read them the riot act, threatened them, and did whatever needed to be done to ensure they voted the right way. I doubt anything like that goes on any more, but it should. Flake, Corker, and the rest of the RINOS should have been dealt with like that.
LBJ could be pretty forceful, but I think it was more a matter of horse trading - promising Senators stuff in exchange for their vote.
During and after the New Deal, Democrats had a lot of stuff they could promise - dams, highways, bridges, bases, etc.
Republicans don't have that much to promise, so they don't get much compliance.
But I don't think Republican senators were much more compliant years ago.
Senators like Javits and Brooke were a lot further off the reservation than today's heretics.
“I doubt anything like that goes on any more”
Oh sure it does, but with the deep state running things now, it's the Patriotic Constitutionalists members that are threatened.
And their wives, children and relatives too.
Corruption runs deep