Sen. Bernie Sanders (I-Vt.) on Tuesday accused former President Trump of “laying the groundwork for election denial” after Trump falsely claimed a photo of a crowd at a campaign rally for Vice President Harris in Detroit was doctored with artificial intelligence (AI) technology.

“Donald Trump may be crazy, but he’s not stupid. When he claims that ‘nobody’ showed up at a 10,000 person Harris-Walz rally in Michigan that was live-streamed and widely covered by the media, that it was all AI, and that Democrats cheat all the time, there is a method to his madness,” Sanders warned in a statement.

“Clearly, and dangerously, what Trump is doing is laying the groundwork for rejecting the election results if he loses,” he said. “If you can convince your supporters that thousands of people who attended a televised rally do not exist, it will not be hard to convince them that the election returns in Pennsylvania, Michigan, and elsewhere are ‘fake’ and ‘fraudulent.’”

“This is what undermining democracy is about. This is what fascism is about,” Sanders added. “This is why we must do everything we can to see that Trump is defeated.”

An estimated 15,000 people attended a rally for Harris, the Democratic nominee for president, and Minnesota Gov. Tim Walz (D), her running mate, at an airport in Detroit last week.

Trump, however, wrote on his social media site, Truth Social, that “She ‘A.I.’d’ it, and showed a massive ‘crowd’ of so-called followers, BUT THEY DIDN’T EXIST!”

Trump insisted “there was nobody there,” even though journalists who covered the event later confirmed thousands of people attended it and pointed to substantial photographic and video evidence to corroborate that it was well-attended.

“Look, we caught her with a fake ‘crowd,’” Trump declared falsely.

The Harris campaign has reported huge turnouts of supporters at other campaign events, such as the 12,000 people who welcomed her at events in Philadelphia and in Eau Claire, Wis., and the 15,000 people who showed up at an event in Glendale, Ariz.