The problem here is that in order to do this, Trump would have to put himself in a dangerous position (dangerous for us, not him).
It's doable, like I said, it's been done by modern politicians, only they're essentially dictators.
If it happened, it would be very, very bad. That he's even talking about it shows what a shit he is.
I don't think it will happen, however if you look at it as a possibility and how it might work.... all he needs to do is amend the Constitution. If he can do that, in the current climate, it's because he's become a dictator.