ANNAPOLIS, Md. — It was early fall, and Donald J. Trump, behind in the polls, seemed to be preparing a rationale in case a winner like him somehow managed to lose. “I’m afraid the election is going to be rigged, I have to be honest,” the Republican nominee told a riled-up crowd in Columbus, Ohio. He was hearing “more and more” about evidence of rigging, he added, leaving the details to his supporters’ imagination.

A few weeks later, Cameron Harris, a new college graduate with a fervent interest in Maryland Republican politics and a need for cash, sat down at the kitchen table in his apartment to fill in the details Mr. Trump had left out. In a dubious art just coming into its prime, this bogus story would be his masterpiece.

Mr. Harris started by crafting the headline: “BREAKING: ‘Tens of thousands’ of fraudulent Clinton votes found in Ohio warehouse.” It made sense, he figured, to locate this shocking discovery in the very city and state where Mr. Trump had highlighted his “rigged” meme.

“I had a theory when I sat down to write it,” recalled Mr. Harris, a 23-year-old former college quarterback and fraternity leader. “Given the severe distrust of the media among Trump supporters, anything that parroted Trump’s talking points people would click. Trump was saying ‘rigged election, rigged election.’ People were predisposed to believe Hillary Clinton could not win except by cheating.”