<<there are no more sane, sober Republicans left. >>
I think you are wrong about that: I know some folks whom I would describe in exactly those terms.  However, none of the people I know personally are in the Congress.  There are so many "back-benchers" in Congress -- especially in the House -- who work in relative obscurity.  I think there must be at least some of them who are horrified by Trump and wrestling with what to do and how to do it.  I hope so.  I don't know that to be true; I hope it is.  Pressure needs to come from voters; nothing moves a politician of any stripe as much as concern for re-election.
It was Republicans who brought the Nixon presidency to an end in 1974.  That didn't seem remotely possible in 1972.