When Donald Trump took the stage at a CNN town hall in Manchester, New Hampshire, one year ago, a crowd of his supporters roared and jeered all through the event, overwhelming the moderator and effectively taking control of the event. President Joe Biden’s advisers noticed. They resolved in private that if Biden ever faced Trump on a debate stage, there would be no one in the peanut gallery. That demand became part of the reelection campaign’s agreed-upon proposal to Trump this week...