The chief problem is that the opposition party is acting that way. As long as that's true, and as long as most people's daily lives look basically the same to them, there's nothing Trump can do that's "too far." He can go on tv and declare himself dictator for life
A major obstacle for folks attempting to defend democracy is that a perfectly accurate description of what Trump is attempting sounds like hysterical conspiracy theorizing to a lot of people. We default to “c’mon, that can’t happen here”—which is exactly why it can.