I have no faith in the military downing tools. Not unless he instructs them to
invade Holland, or nuke Hawaii, or something similarly mental. Part of the reason fascism endures is that it often has the ideological support of the military/police etc. Being inherently authoritarian and all.
Congress and the more conscientious Republicans are the ones most likely to stop him. Which is pretty scary itself, as they've been so power starved they've happily bent over all the way to the toes for him thus far. But we're two years away from the Dems having even a chance to claw back some control, so aside form a benign alien invasion, its probably the best we can hope for.
That said, I may not be nearly as optimistic as Hoo-Rar
@Raoul, but I'll at least give him that the American system is specifically set up to prevent a single President running rough shod over it. The term limit alone is technically a better constitutional safeguard than an old German lady and a bunch of unelected men in silly wigs, in fairness. But it's not infallible by any means. It still needs all branches to do their jobs to a fault. And currently it needs them to do it in the likely face of alt-news demonisation, and probable accusations of traitorism. Unsurprisingly, one of the biggest fascist warning signs imaginable.
Sorry, pre-fascist. Fascist in waiting. Really really scaring right wing authoritarian thing that we can't call fascist yet.