CHICAGO — President Donald Trump is recycling a baseless conspiracy theory to claim that recent protests have been orchestrated by powerful people in “dark shadows” intent on undermining his reelection prospects.

The claims first took root on Facebook and Twitter earlier this year after racial justice protests swelled across the country following the deaths of Black Americans in police custody. Thousands of social media users shared posts suggesting a covert network was coordinating the protests and rioters were descending on communities across the country.

Trump appeared to amplify those unfounded conspiracy theories in an interview with Fox News host Laura Ingraham that aired Monday night, suggesting that protests in Washington during the Republican National Convention were orchestrated by unspecified forces.

“We had somebody get on a plane from a certain city this weekend. And in the plane, it was almost completely loaded with thugs wearing these dark uniforms, black uniforms with gear and this and that,” said Trump, adding that the matter is under investigation.

When asked by reporters Tuesday for additional details on his assertion, Trump said someone else witnessed the activity and he would have to check to see if that person was willing to speak with news media.

Vice President Mike Pence was asked in an interview Tuesday evening to explain what the president was talking about.

“Well, I think what the president’s referring to is actually what we heard in many of the cities. I know in Detroit there were a large number of arrests several weeks ago and the vast majority of people were from out of state. The same thing occurred in arrests that took place in recent cities,” Pence said on Fox News Channel’s “Special Report with Bret Baier.”

The President Has a History of Elevating Online Conspiracy Theories

“Look, there’s something going on here, where the radical left — these anarchists and antifa — are moving people around the country, and it’s one of the reasons that the Justice Department is looking into where is the funding for this coming from? … We’re vigorously investigating where this is being organized from.”

He said during recent rioting that occurred in the nation’s capital, the administration “heard some organization was pre-positioning assets and resources” around the city.

The president has a history of elevating online conspiracy theories from his powerful podium, sometimes amplifying Twitter posts to his 85.6 million followers or dropping references to debunked claims in interviews and appearances. As the November election approaches, he’s been particularly focused on the unproven notion that widespread protests against racist policing are being coordinated and driven by shadowy forces intent on defeating him.

Trump is picking up on unproven conspiracy theories that began spreading earlier this year during protests for racial justice. One of the first public Facebook posts suggesting a similar conspiracy theory appears to have been made in May when Idaho resident Russell D. Wade wrote on Facebook that a plane was transporting protesters from Seattle to Boise, Idaho.

“Be ready for attacks downtown and residential areas,” Wade wrote in a post that has been shared more than 3,500 times. Wade, who lost a bid for local sheriff earlier this year, urged his followers to arm themselves. A social media message sent to Wade on Tuesday was not immediately returned.

Local police departments from Sioux Falls, South Dakota, to Payette County, Idaho, were forced to knock down similar social media rumors in June that “busloads” of rioters were coming to town. Other social media posts claimed that throngs of “antifa,” a term for leftist militants, were plotting to violently disrupt cities and towns.

Trump’s Allies Have Ramped up Their Efforts To Push Similar Uncorroborated Theories Over the Past Week

In Michigan, a limousine businessman had to refute online rumors that his buses were purchased by liberal financier George Soros to coordinate protests after Facebook users manipulated images of his white charter buses to show the words “Soros Riot Dance Squad” emblazoned on the sides.

In Facebook and Twitter posts earlier this summer, Trump also blamed antifa for violence that broke out during racial justice protests. But an Associated Press analysis of court records, employment histories and social media posts for 217 people arrested in Minneapolis and the District of Columbia, cities at the center of the protests earlier this year, found evidence that only a few of those arrested indicated they were involved in left-leaning activities. A few others expressed support for the political right and Trump himself.

Trump’s allies have ramped up their efforts to push similar uncorroborated theories over the past week.

During the Republican National Convention, his personal attorney Rudy Giuliani claimed that “Black Lives Matter and antifa sprang into action” and “hijacked” peaceful protests. Republican Sen. Rand Paul of Kentucky called on the FBI to investigate protests outside of the RNC in Washington last week, describing it as “an organized interstate racket.”

“They need to be arrested, questioned,” said Paul, who had to be escorted to his hotel during the final night of the convention. “The bills need to be subpoenaed by a judge to say, who paid for your bill? How did you get here on a plane, and staying in a fancy hotel, and yet you’re acting like a criminal?”

The messaging from the president and his GOP supporters is aimed at building up fear among voters in hopes of driving them to cast a ballot in the president’s favor this fall, said Jennifer Mercieca, a professor at Texas A&M University who studies what she calls Trump’s “rhetorical genius.”

“Everything is on the line, you have to be sure to vote,” Mercieca said in summing up the message. “They’re out to get you and destroy the American way of life. They’re already here … just a short plane ride away. They’re scary, they wear black.”