How Mr. Trump came to own, operate and then lose the Plaza reveals a lot about his business style. For decades, Mr. Trump has boasted of his boardroom skills in self-exalting speeches and books. As the front-runner in the Republican presidential race, he frequently argues that his corner-office prowess uniquely suits him to negotiate with world leaders.

What does this prowess look like up close? In the Plaza tale, Mr. Trump demonstrated both strengths (an ability to charm or strong-arm, as the occasion required) and weaknesses (a kind of hungry impatience that left him searching for new trophies as soon as one had been acquired). His methods as a political candidate mirror his methods as an executive, say those who have dealt with the latter and seen the former. In fact, the more you know about Mr. Trump’s past, the more his run for high office looks like an effort to close the biggest deal of his life.