At this point the entire party is poisoned, and has been for a while - specifically top-level RNC leadership, donors, etc. Trump is just the current symbol representing the rot that is that quote unquote "party." If it's not him, someone else will step in to fill his role. And will probably be worse.

Reagan was really, really bad. Bush was horrible. Trump was abhorrent. Next step ...

Rejecting Trump is not enough. "Moderate" republicans need to either form their own party or join with democrats. Remaining a republican at this juncture is co-signing anti-democratic ideologies and behavior.