Campaign advisers told Reince Priebus, the Republican National Committee chairman who was helping with debate preparations inside the team’s hotel suite, that Mr. Trump had to leave for a perfunctory “meet and greet.” They feared that Mr. Priebus would object if he knew the truth: Mr. Trump would be appearing on camera with women who had for years accused Bill Clinton of sexual misconduct — a brazen attempt to turn the issue of mistreating women back against the Clinton family.

And those accusers, who had been invited to the debate as surprise Trump guests but had little warning on the fuller itinerary, seemed unsure themselves about what awaited them as they were led into a reception room at the hotel. “I had no idea what we were going in there for,” one of them, Juanita Broaddrick, recalled. “But that doesn’t matter. I would do it all again.”

Before the room’s doors opened to the media and the women were revealed, Stephen K. Bannon, the campaign’s chief executive, shared his vision for the spectacle: “They’re going to rub up on you and be crying,” he remembered telling Mr. Trump. “And you’re going to be empathetic.”

Mr. Trump closed his eyes, Mr. Bannon said, tilting his head back “like a Roman emperor.”

“I love it,” the future president ruled.