President-elect Donald J. Trump recently appeared at a Carrier furnace factory in Indiana and explained why he was there, having worked out a deal to keep some of that company’s jobs from moving to Mexico.

It all happened because he saw something on television: himself.

“About a week ago, I was watching the nightly news,” he said. “I won’t say which one, because I don’t want to give them credit.” (It was NBC.) A Carrier worker had challenged Mr. Trump to keep his promise to stop the manufacturer from leaving the state.

This was news to Mr. Trump, who didn’t believe he had made the promise until the newscast showed video of him doing it. There it was, on TV. So here he was.