WASHINGTON ― President-elect Donald Trump falsely claimed on Sunday that “millions of people” voted illegally in the 2016 presidential election. In a conference call with reporters on Monday, Trump’s campaign team did not produce any evidence to support that allegation.

But the strangest thing about the president-elect’s claim isn’t that there is zero evidence to support it — it’s that Trump, who has turned away daily intelligence briefings since winning the election, took time out of his day to repeat a rumor that initially spread because of one guy on Twitter. (Kellyanne Conway, Trump’s former campaign manager, has said the president-elect is receiving information “from a number of sources.”)

Gregg Phillips, a board member of the conservative anti-voter fraud group True the Vote, tweeted on Nov. 13 that he had “verified more than three million votes cast by non-citizens.” Phillips, who did not respond to a request for comment on Twitter, has not released any data to back up his claims. Snopes, a website that debunks conspiracy theories, reported that its inbox “exploded with messages” asking them to investigate this issue the day after Phillips made that claim.

Phillips’ assertion didn’t spread because of compelling evidence ― he didn’t provide any. And covering up millions of illegal votes would require a massive conspiracy of the sort never seen before. But the internet’s relentless rumor mill amplified Phillips’ claim anyway. Conservative websites like Drudge Report and Infowars elevated his tweets, and as of Monday, one of them had been retweeted more than 9,000 times. It doesn’t seem far-fetched to think that Trump, an avid Twitter user, might have first encountered the claim somewhere on social media.

The Trump campaign did not say where Trump came by the idea that “millions of people” voted illegally. But Trump has repeatedly boosted unfounded conspiracy theories from the dark corners of the internet, whether calling into question President Barack Obama’s birth certificate or entertaining the idea that the late Supreme Court Justice Antonin Scalia might have been intentionally smothered to death with a pillow.

Even True the Vote, the group of which Phillips is a board member, did not repeat his exact claim about 3 million votes.

“We’ll publicly release all our findings when our research is complete,” Catherine Engelbrecht, president of True the Vote, told The Huffington Post in an email Monday.

Phillips’ tweet is “steeped in this ongoing research,” Engelbrecht said, but “we do not plan to publish until every state has appended and published its own voter registry to include 2016 voting information.” (Based on the timing of the tweets, any data to back up Phillips’ claim would have had to come in before states certified their election results, as The Washington Post’s Philip Bump noted on Sunday.)

Asked whether she was aware of anyone publicly making this kind of claim besides Trump and Phillips, Engelbrecht said only that “the erosion of election was a top talking point in the past election, with lots of people saying lots of things. We are glad the issue is getting the attention it deserves.”

The Trump campaign did not offer any evidence to back up the president-elect’s claims during a Monday conference call with reporters. Trump spokesman Jason Miller cited two studies ― but one of them has been debunked, and the other did not investigate what Miller implied it did. In addition, both studies Miller cited were conducted well before the 2016 election. One of them, a 2014 study, was subsequently discredited by peer-reviewed research. The other study, a 2012 Pew report, actually focused on invalid voter registrations, which are different from actual votes.

Asked whether the Department of Justice would investigate Trump’s claim of illegal voting, or if Trump had notified state and local governments of his supposed discovery, Miller dodged the question.

It would, he said, be “inappropriate” for him “to speculate with regard to Justice Department activity before the inauguration, swearing-in and transfer of power.”

UPDATE: 3:40 p.m. ― In a series of tweets on Monday, David Becker, a former director of election initiatives at the Pew Charitable Trusts and the primary author of the 2012 Pew report, confirmed that “we found millions of out of date registration records due to people moving or dying, but found no evidence that voter fraud resulted.”

He added that “voter lists are much more accurate now than when we issued that study in 2012.”