Who’s Afraid of Nikki Haley?

The Iowa caucuses are on Monday, and suddenly Donald Trump’s campaign has made a notable turn. He’s aiming most of his advertising attacks not on Ron DeSantis but at former South Carolina Gov. Nikki Haley. The former President is clearly afraid that a real alternative is gaining on him.

Mr. Trump is running an ad in New Hampshire that Ms. Haley “opposed Trump’s border wall,” and that her “weakness puts us in grave danger.” He’s also hitting his former ambassador to the United Nations on taxes and Social Security, and we’ll parse the merits in a moment.