Mr. Musk is fundamentally a creature of Silicon Valley, a scene that initiated an entire revolution in power dressing. The young masters of that universe dressed down to show that they were members of a new elite — one that refused to dress like the grown-ups they were about to topple. It was the defeat of the suit by the T-shirt.

In front of the White House as he looked over the Tesla vehicles, President Trump said he would not be allowed to drive his new car.

Ethics experts are sounding the alarm that the president's event with Elon Musk could eliminate the lines of proper objectivity from elected officials.