If mitch resigned, would the governor of Kentucky appoint a replacement? The governor of Kentucky is a Democrat.
IIRC he has to pick one from 3 suggested by the Kentucky republican party
The governor is required to replace with another Republican.
As pointed out, the Demonrat Governor is required to appoint a Republican. BUT, he is threatening to ignore that and appoint a Stalinazi Demonrat instead and let it drag through the courts (which I’m sure they could easily find a Derp State judge that would sign off on this).