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.

The head of President Donald Trump’s government efficiency effort, Elon Musk, is emerging as a messaging punching bag for Democrats as they pick up the pieces of their stinging defeat in last year’s elections and search for a winning message for 2026.