As I think I wrote before, last Spring I said to a group of students that the big concerns with a President Trump (which I said was possible but wouldn't happen) wasn't so much that he'd do things like build The Wall or his policies the way we normally think about such things, it's that our system requires some respect for established norms and he wouldn't be bound by any of that.
The other thing about opening up the presidency to a whole new kind of corruption (yes we have plenty of government corruption, even surrounding the executive branch, but just not with the head of state himself), is that it will make impeachment - the only real remedy for that corruption other than voting - a completely political act. Basically, it will be understood that the new norm is that impeachment is something the opposition party does but the president's own party will never do, no matter what the offense. Of course in the true tradition of Both Sides, only Republicans will have the press's blessings to impeach Democrats, and Democrats must keep their powder dry for the good of the country, or something.
tl;dr norms out the window, presidential corruption the new normal, impeachment completely political and expected behavior from opposition parties in Congress with names beginning with 'R'.
Polite fictions we pretend to believe despite all evidence can be a problem, but they at least provide some sense of what should be.