On April 15, the Heritage Foundation's Oversight Project posted a long thread on the social media platform X.
"BREAKING - Flyers distributed at NGO in Mexico encouraging illegals to vote for President Biden," reads the first post. A video shows the flyer hanging in portable toilets at a migrant encampment in Matamoros, just across the Rio Grande from Brownsville, Texas.
The thread quickly racked up more than 9 million views.
"Reminder to vote for President Biden when you are in the United States. We need another four years of his term to stay open," read the last two lines of the flyer in awkward Spanish.
The logo for Resource Center Matamoros (RCM), a local group serving asylum seekers appears on the flyer, as well as the name of its founder, Gabriela Zavala.
Here are the five takeaways from NPR's reporting on the flyer. For a complete account, read NPR's full story.
1. Zavala denies any connection to the flyer or its message
RCM founder Zavala, a U.S. citizen who lives in Texas, says she didn't write the flyer and her group does not encourage migrants to vote. "I was almost in a state of shock," she said about the moment she saw the Heritage thread. "And I said, 'Wow, you know, this is completely untrue.'" She immediately started receiving threats online.
Whoever made the flyer copied text from RCM's website, which has not been updated in years and has outdated information, such as a defunct phone number, that also appears on the flyer.
The first two sentences of the flyer appear to be an old description of RCM copied from the website, which is in English, and run through Google Translate.
The next sentences that discuss voting for Biden are written in a different style and have grammatical errors.
2. The group credited with discovering the flyer visited RCM before the thread published
The Heritage thread says the flyer was discovered by Muckraker, a right-wing video site. Anthony Rubin, the site's founder, often uses undercover tactics in his videos, which portray migration to the U.S. as an "invasion."
Hours before the thread was published, Rubin and his brother, Joshua Rubin, rang the bell at RCM's building.
Anthony Rubin can be heard on security camera footage saying that he and his brother previously worked with migrants "in Colombia, in Panama" and they wanted to volunteer.
Hugo Terrones, RCM's director, met them outside. Terrones called Zavala so Rubin could speak with her.
A snippet from that exchange appears in the Heritage thread with a caption saying "RCM founder Gaby Zavala implied to[Muckraker] that she wants to help as many illegals as possible before President Trump is reelected."
In the clip, Rubin says, "In all honesty, we're just trying to help as many people as possible before Trump gets reelected." Zavala replies, "Believe me, we're in the same boat."
Zavala said the context was volunteering and helping asylum seekers. "And for me, it's like, regardless of who's in office."
Terrones told NPR that Rubin persistently asked him whether he knew of organizations in the U.S. that help migrants vote for Biden, or if he would vote for Biden. Rubin told NPR he does not recall what he asked Terrones.
3. The organizations behind the X thread did not try to verify the flyer with Zavala or RCM before publicizing it
Both Rubin and Mike Howell, the executive director of Heritage's Oversight Project, acknowledged to NPR that they did not ask RCM or Zavala if they had any connection to the flyer before they published the thread.
Rubin told NPR that it "certainly occurred to me" to ask RCM staff to verify the flyer when he visited, but he said he had previously been kidnapped by the Gulf Cartel near there and needed to maintain a low profile.
Howell said he did not reach out to Zavala before publishing the X thread because "it was in the immediate public interest to know about the invasion in the United States." He added, "Would the United States reach out to the CCP [Chinese Communist Party] to verify intelligence about them flooding fentanyl into this country? Of course not."
4. The site where the video shows the flyers is not an RCM location and NPR's reporting found no evidence of flyers
The thread says the site where the video shows the flyers in portable toilets is a "Resource Center Matamoras (RCM) location."
But RCM has not staffed the site in years, a fact confirmed to NPR by other local NGOs. There was once an organized camp at the site but it closed. Aid workers now redirect migrants to shelters.
NPR visited on April 29 and saw an informal encampment where a small number of migrants are staying but did not see any evidence of the flyers.
Migrants at the encampment denied ever seeing the flyers. NPR spoke with migrant aid workers who said they never saw the flyers or heard about them from migrants or volunteers.
NPR saw no evidence of the flyers inside RCM's building. Asylum-seekers who have been there for weeks said they had not seen the flyers or been told to vote in the U.S.
5. This story has implications far beyond the mystery of the flyer
The flyer buttressed a key narrative of former President Donald Trump and his allies, who have made false claims about noncitizens swaying election outcomes since 2016 and have emphasized the issue for months.
Within 12 hours of the flyer appearing online, members of Congress raised it in hearings and used it to justify a push for more restrictive voting laws.
It is illegal for noncitizens to cast ballots in federal elections and studies have repeatedly shown it is very rare.
Despite that, many congressional Republicans are pushing to require documentary proof of citizenship to register to vote. Critics say the proposed laws will make it harder for many eligible U.S. citizens to register and vote.
Jared Holt, a senior research analyst at the Institute for Strategic Dialogue, told NPR that false narratives about migrants voting could be used later by those who may want to undermine election results.
"If the ground is being seeded with claims like these," said Holt, "Then that may very well be another possible avenue to try to delegitimize democratic processes in this country."
