The only two Democrats who might cross over would be the ones in Alabama (Doug Jones) and in West Virginia (Joe Manchin), but Jones may think he is going to lose anyway, and Manchin isn't up for re-election until 2024 so he may figure that how he votes in 2020 will be long forgotten by then.
Eisenhower named a Supreme Court justice in October 1956 when he was running for re-election. Of course there probably weren't a lot of people who expected him to lose to Adlai Stevenson.