Donald Trump thinks he’s identified a crucial mistake of his first term: He was too nice. We’ve been talking for more than an hour on April 12 at his fever-dream palace in Palm Beach. Aides lurk around the perimeter of a gilded dining room overlooking the manicured lawn. When one nudges me to wrap up the interview, I bring up the many former Cabinet officials who refuse to endorse Trump this time. Some have publicly warned that he poses a danger to the Republic. Why should voters trust you, I ask, when some of the people who observed you most...