That afternoon, Mr. Limbaugh was also onto the story, telling his audience, “Comey said, under Senate oath, he had never been pressured to halt any investigation.” As evidence, Mr. Limbaugh read straight from the GotNews.com article. The whole Russia investigation, he declared, is “a political witch hunt.”

That account of the Comey testimony has lived on in the weeks since, with Sean Hannity of Fox News citing it as recently as Tuesday night. “And by the way,” he insisted on his program, “James Comey also said it never happened.”

What actually happened in the Judiciary Committee hearing was hardly an exonerating moment for Mr. Trump. Senator Mazie K. Hirono, Democrat of Hawaii, asked Mr. Comey whether “the attorney general or senior officials at the Department of Justice” had ever tried to halt an investigation. Mr. Comey, then still the F.B.I. director, said they had not.

Never did Ms. Hirono ask Mr. Comey anything about Mr. Trump in that exchange, nor did Mr. Comey volunteer anything about the president’s words to him. (Mr. Posobiec insisted that he had misrepresented nothing, saying Mr. Comey’s comments “certainly could include President Trump, who is the senior official of the entire executive branch.”)

Mr. Trump has had no small role in the elevation and legitimization of dubious news accounts and the sources that spread them — he is both consumer and enabler.

The president has shared discredited information from his Twitter account on subjects like voter fraud. He has publicly embraced those who trade in these kinds of theories, appearing, for instance, on Mr. Jones’s radio program while he was running for president. And after the election, he called Mr. Jones to thank him for his support.

Mr. Trump has been seen reading material from GotNews.com, an outlet founded by Charles C. Johnson, who has also helped start a crowdfunding website that pays for private investigations and legal defenses for fringe conservative causes. Among its current campaigns is one to help a man accused of sending a journalist with epilepsy a Twitter graphic that triggered a seizure.