I actually think President Pence is an inevitability. Even if Trump manages to survive his full term, I bet this occurs:
Nov 3, 2020: Trump loses in a landslide.
Nov 2020-Jan 2021: Trump throws one of his fits, whines constantly about the media, makes accusations of vote fraud and everything under the sun, meanwhile people in Congress and various prosecutors hint he might be facing charges.
Jan. 18, 2020: Trump resigns, President Pence sworn in.
Jan. 19, 2020: President Pence pardons Trump and all his cronies.
Jan. 20, 2020: New President sworn in.
What a way to kneecap Republicans going into a favorable 2022 midterm.
Favorable? Have you seen the Senate map?
Incumbent Democratic president probably. Republicans should be able to make decent gains in the house (especially if the Dems made gains in 2018 and/or 2020) and atleast retain all of their senate seats.