On Friday morning, the president of the United States tweeted about a two-day-old Washington Examiner article with an unsubstantiated claim from one anonymous rancher.

“There’s a lot of people coming in not just from Mexico,” the rancher had told the newspaper. Then, without offering further proof, the rancher said that “people, the general public, just don’t get the terrorist threats of that. That’s what’s really scary. You don’t know what’s coming across. We’ve found prayer rugs out here. It’s unreal. It’s not just Mexican nationals that are coming across.”

Trump quoted the line about prayer rugs, adding: “People coming across the Southern Border from many countries, some of which would be a big surprise.”

The anonymous rancher’s comment about prayer rugs — one that has now been repeated by the president to support his proposed border wall during the partial government shutdown — is similar to the claims of a conspiracy theory that has long been popular with far-right and anti-Muslim figures and publications. And the rumor itself has been invoked to support a larger, debunked claim from a far-right group that Islamic State operatives have established a massive training camp at the border.

It is a claim that conflates an item used by some practicing Muslims with a sign of terrorists — the false implication being that any association with the Islamic faith is itself worthy of suspicion.

Ibrahim Hooper, a spokesman for the Council on American-Islamic Relations, said the meme was “Islamophobic.”

“It exploits the Islamophobia promoted by the president himself,” Hooper told The Washington Post, “and it dog whistles that anything associated with Islam is somehow connected to terrorism.”

“Even if there were prayer rugs at the border, so what? That isn’t any indication of anything except that there may have been a Muslim trying to cross the border,” he added, noting that Trump is simply “trying to distract from his own legal and political problems.”

Below is a short history of the prayer rug rumors, their debunking, and their reanimation during border security conversations over the years.

2005: “Suspicious items picked up by local residents”

The first time rumors of Muslim prayer rugs at the border appear to have crossed over into notable media coverage was in 2005. Some Republican lawmakers advocating for increased border security invoked the rumor to support their policies.

In a statement, then-senator Kay Bailey Hutchison (R-Tex.) cited the following as evidence of terrorist threats along the southern border: “Along the Mexican border there have been stories of suspicious items picked up by local residents, including Muslim prayer rugs and notebooks written in both Arabic and Spanish,” the statement read. There was no specific incident or photograph to accompany the claim, which would become a running theme with this rumor.

Later that year, then-representative Tom Tancredo (R-Colo.) told CBS News for a story on border threats that during a recent visit to the border: “We found the Koran. We found copies of the Koran. We have found prayer rugs.”

A 2005 fact check of a TV ad claiming that terrorists were slipping across the southern border found that there were immigrants of Middle Eastern descent crossing into the U.S. through Mexico, but basically no proof any of them were connected to a terrorist group. The ad was intended to rally support for building a “fence” along the border.

2014: Breitbart publishes a picture

Nearly a decade later, the rumor would become news again after a group of security contractors working at the border found a piece of cloth on the ground and sent a photo to the conservative news site Breitbart, which ran it along with the following quote from an unnamed security contractor:

“I saw this thing laying around. And I was like, ‘What the hell is that?’ We walked over there and I didn’t really want to pull at it not knowing what was on it. I poked a bit at it with a stick and noticed some of the Arabic writing and was just like, ‘Oh boy.’ I snapped a couple of photos and then went on our patrol.”

A thorough analysis of the image, however, indicates that the cloth was probably a soccer jersey.

David Dewhurst, then the lieutenant governor of Texas, repeated the prayer rug claim twice in 2014 to support his belief that the Islamic State was using the border to cross into the U.S.

“Prayer rugs have recently been found on the Texas side of the border in the brush,” he said at a Values Voter Summit in D.C. that year. Dewhurst’s spokesman cited the Breitbart story and a radio interview as evidence to support his claim, which PolitiFact ultimately rated as “pants on fire.”

The radio interview cited Judicial Watch, a conservative group that cited anonymous sources claiming there are secret Islamic State training camps along the border.

When PolitiFact contacted several law enforcement agencies in 2014 about these long-running reports, they were uniformly told that there were no reports of prayer rugs found at the border.

And as we noted in 2014, national law enforcement and local officials both debunked this claim, but not before the allegation was picked up by a number of conservative outlets, including One News Now, American Thinker and the Washington Times.

2019: An anonymous rancher

The Washington Examiner interview cited by Trump appears very similar to these previous, debunked claims. The Trump administration, despite clear evidence otherwise, also has repeatedly claimed that terrorists were using the southern border to enter the United States. The State Department has debunked those claims twice, most recently in September:

“At year’s end there was no credible evidence indicating that international terrorist groups have established bases in Mexico, worked with Mexican drug cartels, or sent operatives via Mexico into the United States. The U.S. southern border remains vulnerable to potential terrorist transit, although terrorist groups likely seek other means of trying to enter the United States,” the State Department said.

The Post reached out to a number of ranchers in southwestern New Mexico, not far from the U.S.-Mexico border. Many said they had heard rumors about prayer rugs being found on properties near the border, but most had not personally seen them. Most also spoke on the condition of anonymity, for a variety of reasons.

Only one rancher, who owns more than 100,000 acres about 50 miles from the border, said he has found such items on his land over the years, but, he said, they were faded and had rotted so he does not know whether they were prayer rugs or just blankets.

Another rancher said that even if prayer rugs were being found on their properties, it may not be discussed because it’s not at all uncommon for land owners in the area to stumble upon trash, debris and belongings that have been left behind from apparent immigrants and drug smugglers.

Judy Keeler, who grew up on a ranch and has owned her own for decades, said that over the years, land owners in the area have also been confronted with the collateral damage; she said neighbors have reported finding dead bodies on their land, and her own family has had to help a number of people who were left stranded by human traffickers attempting to smuggle them into the country.

Keeler and several others expressed their concerns and their desire for tighter border security.

“I’m not in favor of high walls,” she told The Post, “but we do need to secure the borders.”

Meanwhile, others have pointed to alternative explanations that would explain the presence of blankets on the border.