Donald Trump couldn’t resist commenting on the news that Democratic Senator Dianne Feinstein was the target of Chinese spying, but he missed the main point.

“I like Dianne Feinstein, I have to tell you, but I don’t like the fact she had a Chinese spy driving her, and she didn’t know it,” Mr. Trump averred at a Saturday rally in Ohio, adding: “Then she says to me: ‘Well, what did you know about this and that [Russia collusion]?’ I mean, give me a break, c’mon folks.”

But...