I dunno, in both cases I would say “just go already!”
I mean is a ruby-red state like OK going to appoint a Dem to fill Imhoff’s seat? Is deep-blue California going to appoint a GOP’er to fill Feinstein’s? How likely is that? Maintaining a partisan edge for one’s team really can’t explain either case. Gotta be ego, and anyone with that much of an ego problem probably doesn’t belong in office in the first place.