The Post's Michelle Ye Hee Lee explains why White House press secretary Sean Spicer's claims on Jan. 24 about voter fraud in the presidential election don't add up. (Bastien Inzaurralde/The Washington Post)

President Trump continues to say he believes that 3 million to 5 million ballots were illegally cast during the election, his press secretary said on Tuesday, without providing evidence to back up the president's claim, which is not supported by any verifiable facts.

“The president does believe that. He has stated that before,” press secretary Sean Spicer said during a briefing on Tuesday afternoon. “I think he stated his concerns, voter fraud and people voting illegally, during the campaign. And he continues to maintain that belief based on studies and evidence that people have presented to him.”

Spicer was repeatedly pressed by reporters to provide this evidence, and he pointed to just one study and cited a statistic that is not found in that study.

Spicer said that a 2008 Pew study “showed 14 percent of people who have voted are noncitizens.” Spicer was likely referring to a study that members of his team frequently cite in trying to back up their claims of voter fraud, the 2012 Pew Center on the States study that looked for ways to make the election system more accurate, cost-effective and efficient, and found that many voter registrations were significantly inaccurate or no longer valid because people moved, had died or were inactive voters — although they found no evidence that this led to voter fraud. That study did not examine the citizenship of voters.

There's another study frequently referenced by Trump aides that does look at citizenship, although its findings and methodology have been challenged by fellow researchers. Old Dominion University professors studied voting participation rates of noncitizens by using data from 2008 and 2010 collected through the Cooperative Congressional Election Studies and concluded that 14 percent of noncitizens surveyed in 2008 and 2010 said they were registered to vote. The professors warned that “it is impossible to tell for certain whether the noncitizens who responded to the survey were representative of the broader population of noncitizens.”

Months before the election, Trump warned that he could lose because of widespread voter fraud, even though elections officials and experts said such concerns were unfounded. Since winning the electoral vote, Trump has continued to claim that he would have also won the popular vote had it not been for illegally cast ballots, even though there is no evidence of them.

At a reception for congressional leaders on Monday, Trump claimed that between 3 million and 5 million illegal votes caused him to lose the popular vote to Hillary Clinton, according to people familiar with the meeting. Analyses of the election found virtually no confirmed cases of voter fraud, let alone millions. Clinton won the popular vote by more than 2.8 million votes.

Spicer said there are no plans to investigate this alleged voter fraud at this point, as the president is confident that he is the winner of the election. Spicer wouldn't say if he himself believes that there were millions of illegal votes cast.

“The comment that he made was, he said 3 to 5 million people could have voted illegally based on the studies that he’s seen,” Spicer said. “But he’s very clear that he won the election based on the 306 electoral votes that he got. We're here on Day 2. Let's not prejudge what we may or may not do in the future.”

Later Spicer added: “He's very comfortable with the depth and breadth of the support that he got from the American people.”

At one point during the briefing, NPR national political correspondent Mara Liasson pressed Spicer on why the administration isn't investigating this fraud if it truly believes it occurred.

“If 3 to 5 million people voted illegally, that is a scandal of astronomical proportions,” Liasson said. “Doesn't he want to restore Americans' faith in their ballot system? Wouldn't he want an investigation of this? I mean, this is a huge, huge scandal.”

“But, Mara, as I've noted several times now, he's believed this for a long time, and I think he won fairly overwhelmingly,” Spicer said.

“I'm asking you: Why not investigate something that is the biggest scandal in American electoral history?” she said. “Three to 5 million people voting illegally?”

“Maybe we will,” Spicer said. “We'll see where we go from here, but right now the focus that the president has is on putting Americans back to work. It was a comment that he made on a long-standing belief.”

David Nakamura contributed to this report.