1) The republicans lose the house and senate in 2018.
2) The speaker of the house, third in line to the presidency does NOT have to be a member of the house.
3) The dims appoint the hildabeast as speaker and they start impeachment proceedings against President Trump.
4) Once they railroad President Trump, they railroad President Pence.
5) If he hasn't designated a VP then the hildabeast becomes madame president, a wet dream for libs and marxists everywhere.
That is as likely to happen as any of the other scenarios.
She would outdo so many of the earlier Presidents. More corrupt than LBJ. More unlikable than Nixon. More clueless than Harding.
If Pence did become President and nominated someone as the new VP, the Democrats (if they controlled Congress) could prevent the nominee from being confirmed.
Impeachment is only an indictment. Removal requires a 2/3rds majority (67 votes)in the Senate to Convict and Remove from office.
Very, very high threshold!