Donald Trump has bought into the unfounded rumor that the families of New York City’s 9/11 victims don’t want Mayor Zohran Mamdani at the tragedy’s twenty-fifth anniversary ceremony in September.When asked about the conspiracy during a White House press conference Wednesday, Trump claimed that he “understood” why there was pressure to keep Mamdani away from the event, telling a reporter that the victims’ families were “very unhappy with the mayor.”“I think they’re having a hard time with Mandami,” Trump said, pronouncing the New York City mayor’s name wrong. “The people having to do with—anybody having to do with 9/11 right now, on the victims’ side, and there’s a lot of them, they’re very unhappy with what’s going on in New York.”The conspiracy appears to have come from a New York Post headline, published on the Sunday edition’s front page, that claimed “thousands of 9/11 families” wanted Mamdani banned from the ceremony.But that’s not true: The Rupert Murdoch–owned paper cited a Change.org petition launched by Giovanni Galante as the origin point of the startling figure. But Galante, who lost his wife Grace Catherine Galante in the attacks, didn’t have the signatures to back up that claim.The petition argued that Mamdani’s reluctance to condemn the phrase “globalize the intifada”—which pro-Palestinian activists have used as a universal call for Palestinian liberation from Israeli occupation—should disqualify him from attendance, as it suggests he does not “share American values” with the victims’ families.The petition has since accrued 42,000 “verified signatures,” though that simply means the electronic sign-offs were conducted by a person rather than a bot. It does not ensure the signatures came from New Yorkers—let alone the families of the nearly 3,000 people who died during the Al Qaeda terrorist attack.In an interview with Popular Information, Galante said that no such list actually existed.“We don’t have a list,” Galante told the independent digital newsletter.Even the Post story contradicted its headline’s wild claim, reporting that the petition had “collected over 1,100 signatures in a little over a week, including from at least 300 victims’ families.” But the Post interviewed just three sources who lost a family member during the attack and also signed the petition.In reality, the 300 figure reported by the Post was also the result of guesswork based on the petition’s popularity.“We all know each other, so … think about it. If you know 10 people and they give it to 10 more people they know that lost. That’s how we got the 300 number,” Galante said. “I don’t go through the list and look at the names.”Nonetheless, the story was quickly cannibalized by right-wing media, finding plenty of air time across Fox News’s myriad properties and even spreading to CBS News.“Thousands of 9/11 victims’ families are asking New York City Mayor Zohran Mamdani not to attend this year’s solemn remembrance ceremony,” CBS reported Monday before issuing a retraction.Mamdani, meanwhile, has no plans to stay away from the event.“I will proudly honor the families, the survivors, the first responders forever impacted by that horrific terror attack by standing alongside them at this year’s 9/11 commemoration, reaffirming that we will never forget the solemn day felt by all of us who call this city home and, frankly, by all of us who called this country home,” Mamdani said.In a statement to CBS News, the 9/11 Memorial & Museum noted that it had “intentionally worked to keep the commemoration free of politics. Government officials from across the political spectrum have attended the ceremony simply to bear witness.”