Like millions of people around the world, I was reassured to learn that Donald Trump is a “Very Stable Genius.” You see, if he weren’t — if he were instead an erratic, vindictive, uninformed, lazy, would-be tyrant — we might be in real trouble. Let’s be honest: This great nation has often been led by mediocre men, some of whom had unpleasant personalities. But they generally haven’t done too much damage. The president spends his mornings watching TV and rage-tweeting. But it’s early days. We spent more than two centuries building a great nation, and even a very stable genius probably needs a couple of years to complete its ruin.