Let’s examine a few scenarios:
I. Trump resigns or leaves office prior to the completion of an investigation.
I.A Pence becomes President under the 25th.
I.B Pence nominates and both chambers have to agree upon a new Veep. This veep is a tie-breaker in the Senate, so it will happen sooner instead of later. Who has already been vetted and voted for by a lot of people? McCain.
This is good for John McCain.
II. Impeachment happens, conviction happens, and Trump is removed from office. Pence becomes President. See I.A and I.B.
This also, is good for John McCain.
III. Impeachment happens before the 2018 GE but manages to bring Pence into it because of his ties to Manafort and (alleged) lies about Flynn.
III.A Ryan becomes President under the 25th.
III.B Ryan nominates McCain (because he sure as shootin’ isn’t going to nominate Romney!) because Ryan has no foreign policy chops at all. Both chambers agree.
This is good for John McCain.
IV. Impeachment and conviction happens, but after the 2018 midterms. Trump is removed and we have a President Pence.
IV.A If there is only one Democratic chamber, someone who can get past BOTH chambers is going to have to be nominated by Pence and then placed in the Veep slot. Remember, an investigation will still be proceeding on Pence. Hence, I suspect strongly it will be McCain.
This is good for John McCain.
IV.B There are TWO Democratic chambers. President Pence will have to pick someone that the Dems like, but won’t cause his own party to come after him. Beats the daylights out of me who they pick.
This is NOT good for John McCain, but he still keeps his Senate seat.
V. Impeachment and conviction manage to happen after the 2018 midterms involving BOTH Trump and Pence. Pelosi becomes President.
V.I A Democratic nominee is proposed for Veep. Obviously it isn’t John McCain, but it also isn’t someone critical to a majority in the Senate.
Not great for John McCain, but he still keeps his Senate seat.
VI. Trump resigns AFTER the 2018 midterms and there are Dems in charge of one or more chambers. This is the same as case IV, above.
50-50 for John McCain.
As we get into increasingly unlikely scenarios, it becomes less good for John “yells at clouds” McCain, but in several of these cases, especially the more likely case of Trump bailing before a trial, McCain becomes veep.
Do I like it? No. But the man has a measurable chance of ending up at the Naval Observatory.