Months after that inaugural episode in January 2004, Mr. Trump filed his individual tax return reporting $89.9 million in net losses from his core businesses for the prior year. The red ink spilled from everywhere, even as American television audiences saw him as a savvy business mogul with the Midas touch.

Twelve years later, that image of the self-made, self-saved mogul, beamed into the national consciousness, would help fuel Mr. Trump’s improbable election to the White House.

But while the story of “The Apprentice” is by now well known, the president’s tax returns reveal another grand twist that has never been truly told — how the popularity of that fictional alter ego rescued him, providing a financial lifeline to reinvent himself yet again. And then how, in an echo of the boom-and-bust cycle that has defined his business career, he led himself toward the financial shoals he must navigate today.

Mr. Trump’s genius, it turned out, wasn’t running a company. It was making himself famous — Trump-scale famous — and monetizing that fame.