The United States needs a president with the mental and emotional acuity to react in crisis in a way that will provide confidence and faith in the people he stewards. In the midst of an apparent assassination attempt, Trump rose to his feet, and the first thing that he did was pump his fist in the air and mouth the word “fight.” It was very King Arthur-esque. Obviously, the story was still developing Saturday night, and it’s possible that the known facts will change — maybe drastically. But what’s clear now is that no one has to question Trump’s fitness for office. Meanwhile, President Joe Bi…