I don't think any of them are realistic - except for a partially successful military coup that succeeds in breaking the chain of command but leaves the President or Vice President alive and at liberty, protected by loyal elements of the military.
The constant posting here of how much "the military" supports Trump is misinformed. Yes, he has support in the military. He also has enemies.
Some of those enemies control large bodies of troops.
One Trident sub can ruin a Democrat would-be dictator’s whole day.
What happens if a sub nukes a dozen blue cities?
There goes the population advantage of the Dems.
And food production, and much of the red voters, being widely dispersed, are not immediately effected.
Remember, it was DEMOCRAT Eric Swallows-well who said he’d nuke Red State voters.
As a candidate.
In public.
He wasn’t merely considering hypotheticals in an internet discussion.