They Don't.
Nancy; "see, I/we did the right thing but they won't resign and since this is America, I can't force them."
“Nancy “orders” them to resign. “
Nancy can’t order them to do anything. She can suggest, which she has done. But what this means is that the Democratic machine will likely find, develop and finance a primary challenger. While it is possible for the existing candidate to win anyway, Joe Lieberman is an example, it is unlikely in these two cases. It is likely that one or both of them will negotiate a deal where they go off to some university job with plenty of money and perks.
There are two “retirement” paths for connected Democrats. They are shunted off to a college someplace or they become lobbyists. The alternative is a gun cleaning accident.