In a video posted to Facebook on Sept. 14, Dan Bongino, a popular right-wing commentator and radio host, declared that Democrats were planning a coup against President Trump on Election Day.
For just over 11 minutes, Mr. Bongino talked about how bipartisan election experts who had met in June to plan for what might happen after people vote were actually holding exercises for such a coup. To support his baseless claim, he twisted the group’s words to fit his meaning.
“I want to warn you that this stuff is intense,” Mr. Bongino said, speaking into the camera to his 3.6 million Facebook followers. “Really intense, and you need to be ready to digest it all.”
His video, which has been viewed 2.9 million times, provoked strong reactions. One commenter wrote that people should be prepared for when Democrats “cross the line” so they could “show them what true freedom is.” Another posted a meme of a Rottweiler about to pounce, with the caption “Veterans be like … Say when Americans.”
The coup falsehood was just one piece of misinformation that has gone viral in right-wing circles ahead of Election Day on Nov. 3. In another unsubstantiated rumor that is circulating on Facebook and Twitter, a secret network of elites was planning to destroy the ballots of those who voted for Mr. Trump. And in yet another fabrication, supporters of Mr. Trump said an elite cabal planned to block them from entering polling locations on Election Day.
All of the rumors appeared to be having the same effect: riling up Mr. Trump’s restive base, just as the president has publicly stoked the idea of election chaos. In comment after comment about the falsehoods, respondents said the only way to stop violence from the left was to respond in kind with force.
“Liberals and their propaganda,” one commenter wrote. “Bring that nonsense to country folks who literally sit in wait for days to pull a trigger.”
The misinformation, which has been amplified by right-wing media such as the Fox News host Mark Levin and outlets like Breitbart and The Daily Wire, adds contentiousness to an already powder-keg campaign season. Mr. Trump has repeatedly declined to say whether he would accept a peaceful transfer of power if he lost to his Democratic challenger, Joseph R. Biden Jr., and has urged his supporters “to go into the polls and watch very carefully.”
The falsehoods on social media are building support for the idea of disrupting the election. Election officials have said they fear voter harassment and intimidation on Election Day.
“This is extremely concerning,” said Megan Squire, a computer science professor at Elon University in Elon, N.C., who tracks extremists online. Combined with Mr. Trump’s comments, the false rumors are “giving violent vigilantes an excuse” that acting out in real life would be “in defense of democracy,” she said.
Tim Murtaugh, a Trump campaign spokesman, said Mr. Trump would “accept the results of an election that is free, fair and without fraud” and added that the question of violence was “better put to Democrats.”
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In a text message, Mr. Bongino said that the idea of a Democratic coup was “not a rumor” and that he was busy “exposing LIBERAL violence.”
Distorted information about the election is also flowing in left-wing circles online, though to a lesser degree, according to a New York Times analysis. Such misinformation includes a viral falsehood that mailboxes were being blocked by unknown actors to effectively discourage people from voting.
Other popular leftist sites, like Liberal Blogger and The Other 98%, have also twisted facts to push a critical narrative about Republicans, according to PolitiFact, a fact-checking website. In one inflammatory claim last week, for instance, the left-wing Facebook page Occupy Democrats asserted that Mr. Trump had directly inspired a plot by a right-wing group to kidnap Gov. Gretchen Whitmer of Michigan.
Social media companies appear increasingly alarmed by how their platforms may be manipulated to stoke election chaos. Facebook and Twitter took steps last week to clamp down on false information before and after the vote. Facebook barred groups and posts related to the pro-Trump conspiracy movement QAnon and said it would suspend political advertising postelection. Twitter said it was changing some basic features to slow the way information flowed on its network.
On Friday, Twitter executives urged people “to recognize our collective responsibility to the electorate to guarantee a safe, fair and legitimate democratic process this November.”
Of the lies, Facebook said it was “removing calls for interference or violence at polling places” and would label posts that sought to delegitimize the results. YouTube said it was not recommending videos containing the false rumors, while Twitter said sharing links to disputed news stories was permitted if the tweets did not violate its rules.
Even so, the idea of a Democrat-led coup has gained plenty of traction online in recent weeks. It has made its way into at least 938 Facebook groups, 279 Facebook pages, 33 YouTube videos and hundreds of tweets, a Times analysis found.
The unfounded claim traces back to an Aug. 11 letter from two former military officers, John Nagl and Paul Yingling, to the country’s top military official, Gen. Mark A. Milley, according to researchers at the Institute for Strategic Dialogue, a London-based research organization. In their public letter, Mr. Nagl and Mr. Yingling asked General Milley to have military forces ready to escort Mr. Trump from the White House grounds if he lost the election and refused to leave.
Some online commentators seized on the letter as evidence of a coming left-wing coup. “Bootlickers Nagl and Yingling suggest a violent military coup,” read one post on Facebook on Aug. 12, which got 619 likes and comments and linked to the letter. That same day, Infowars, a conspiracy theory website, also published a piece claiming that retired Army officers were openly talking about a coup by Democrats.
Mr. Nagl and Mr. Yingling did not respond to requests for comment.
On Sept. 4, the right-wing outlet The National Pulse added to the conspiracy. It published a piece pointing to what it said were the “radical, anti-democratic tactics” of the Transition Integrity Project, a bipartisan group of former government officials who analyzed how to prevent a disrupted presidential election and transition. The group published a report on Aug. 3 about its efforts, but The National Pulse said the document showed “an impending attempt to delegitimize the election coming from the far left.”
Trey Grayson, a Republican former secretary of state of Kentucky and a member of the Transition Integrity Project, said the idea that the group was preparing a left-wing coup was “crazy.” He said the group had explored many election scenarios, including a victory by Mr. Trump.
Michael Anton, a former national security adviser to President Trump, also published an essay on Sept. 4 in the conservative publication The American Mind, claiming, “Democrats are laying the groundwork for revolution right in front of our eyes.”
His article was the tipping point for the coup claim. It was posted more than 500 times on Facebook and reached 4.9 million people, according to CrowdTangle, a Facebook-owned analytics tool. Right-wing news sites such as The Federalist and DJHJ Media ramped up coverage of the idea, as did Mr. Bongino.
Mr. Anton did not respond to a call for comment.
The lie also began metastasizing. In one version, right-wing commentators claimed, without proof, that Mr. Biden would not concede if he lost the election. They also said his supporters would riot.
“If a defeated Biden does not concede and his party’s rioters take to the streets in a coup attempt against President Trump, will the military be needed to stop them?” tweeted Mr. Levin, the Fox News host, on Sept. 18. His message was shared nearly 16,000 times.
After The Times contacted him, Mr. Levin published a note on Facebook saying his tweet had been a “sarcastic response to the Democrats.”
Bill Russo, a spokesman for the Biden campaign, said in a statement that Mr. Biden would accept how the people voted. “Donald Trump and Mike Pence are the ones who refuse to commit to a peaceful transfer of power,” he said.
On YouTube, dozens of videos pushing the false coup narrative have collectively gathered more than 1.2 million views since Sept. 7, according to a tally by The Times. One video was titled “RED ALERT: Are the President’s Enemies Preparing a COUP?”
The risk of misinformation translating to real-world action is growing, said Mike Caulfield, a digital literacy expert at Washington State University Vancouver.
“What we’ve seen over the past four years is an increasing capability” from believers to turn these conspiracy narratives “into direct physical actions,” he said.
Ben Decker contributed research.