After a clear conspiratorial narrative about the attempted “coup” was established and promoted by mainstream conservative outlets, the work of online amplification began. One of its driving voices, Tom Fitton, the president of Judicial Watch, the conservative group that recently sued the Justice Department for records on Mr. Biden and Ukraine, has participated heavily in hyperpartisan social media communities to further amplify the claim.

For instance, on r/The_Donald, a quarantined community of the online bulletin board Reddit, supporters of the president often trade in disinformation and coordinate the spread of pro-administration conspiracy theories across different platforms. There, Mr. Fitton has posted 79 times since the beginning of September, rallying members by encouraging them to tune into Mr. Hannity’s show to learn about the coup conspiracy, and generally pushing the theory as a hot-button issue.

Mr. Fitton said in an interview that President Trump had faced constant lawless and constitutional harassment by Congress. He added that the quarantine of r/The_Donald — which warns readers about the forum’s content — was “convenient” and that Twitter was a “more impactful” medium these days.

The coup conspiracy stretches “across platforms as the president’s followers are on social media such as Reddit, Twitter, Instagram and YouTube,” Professor Grygiel said. “But it is important to remember that he is the one in power. He uses feedback from these platforms and communities to his advantage.”

Indeed, Mr. Trump’s claims of a coup date back as early as the beginning of this year, even arguing that the investigation led by Robert S. Mueller III into Russia’s election interference was an “attempted coup.” Mr. Trump has referred to coups seven times on Twitter during his presidency, all in 2019, and many times the claims were cut from segments on right-wing cable news.

The claims grew in the last week. Talk of a “coup” became common among guests on Fox News, including on programs as varied as daytime talk shows like “Outnumbered” and “The Five,” and more widely watched prime-time shows like “The Ingraham Angle.”

“It’s no accident,” said Doug Heye, a former spokesman for the Republican National Committee. “I’ve been hearing this word being used for well over a year now and in part because it’s really seeped through on conservative media.”