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.

Elon Musk has faced "great difficulty" running his companies while trying to remake the US government. Some observers worry he's taken on too much.

With Tesla's stock price plunging, the president made a bombastic announcement in support of "truly great American" Musk.