> I disagree that Trump would be such a shoe-in for 2020. The Democrats just need a better candidate.
Note that it's almost unheard-of for the sitting president not to run for a second term. (I certainly can't remember a case in my short life.) So either Trump or Clinton will almost certainly be on the ballot in 4 years.
If Hillary isn't in a relatively strong position by 2020, I suspect she'd be reasonable enough to switch with someone else.
LBJ didn't run for reelection.
I think with the currently developing scandals (especially sexual assault allegations), and likely many more scandals between 2016 and 2020, they'd need someone even less liked than Hillary for him to have a shot.
The bigger threat is indeed whatever media empire he might try to launch after the election. (Scarily, I could picture him doing so whether he wins or loses.)