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.

Instead of the presidential motorcade of large, black SUVs lined up on the driveway of the South Lawn, there were five Teslas for Trump to peruse. Trump announced his intention to buy a Tesla on Monday night to support his close adviser billionaire Elon Musk,