Steven Bannon, the influential Trump adviser who has long been critical of Musk, crowed that the tech billionaire’s attacks on Trump were so personal that he won’t be forgiven by the MAGA crowd. “Only the fanboys are going to stick with him—he’s a man without a country,” Bannon told us.

But Mr. Trump’s warnings to his former ally are backed by several ways the White House could punish the world’s richest man.