2/3 required to convict.
However, you have to consider the number of current "D" senators who will be sharing the same fate as Montana's own JohnBoy Tester:
Trump carried Montana by double digits.
Each..and..every statewide office went flaming Red and both houses of the State Legislature will have R super majorities.
No big deal?
Tester can count, he's now the Number One target for replacement in Montana even if he sets his foot exactly right each and every day until '24 and he knows it.
I wouldn't be shocked to hear Tester resign to take a job on K Street. Might not be the only one.