Anyone who thinks the GOP primary in 2020 will look like the GOP primary in 2016 is first of all not taking into account Trump may not be on the ballot in 2020 and second that if he is, his challengers—with little to lose—may choose to attack him as a liar, criminal, and traitor
2/ I'm sure some will respond to this tweet by saying no, no one in the GOP would ever attack Trump in this way, but remember that by 2020 the Mueller report will be out and some of Trump's challengers will be guys with no political future at 1% in the polls with nothing to lose
3/ Incidentally, this is one reason state GOP officials like those in South Carolina are trying to cancel their primaries altogether, because anyone who gets on that stage with Trump (if Trump is even there) will be able to say things about him that are humiliating and *damaging*
