A man who President Donald Trump has promoted as an authority on voter fraud was registered to vote in multiple states during the 2016 presidential election, the Associated Press has learned.

Gregg Phillips, whose unsubstantiated claim that the election was marred by 3 million illegal votes was tweeted by the president, was listed on the rolls in Alabama, Texas and Mississippi, according to voting records and election officials in those states. He voted only in Alabama in November, records show.

In a post earlier this month, Phillips described "an amazing effort" by volunteers tied to True the Vote, an organization whose board he sits on, who he said found "thousands of duplicate records and registrations of dead people."

Trump has made an issue of people who are registered to vote in more than one state, using it as one of the bedrocks of his overall contention that voter fraud is rampant in the U.S. and that voting by 3 to 5 million immigrants illegally in the country cost him the popular vote in November.

The AP found that Phillips was registered in Alabama and Texas under the name Gregg Allen Phillips, with the identical Social Security number. Mississippi records list him under the name Gregg A. Phillips, and that record includes the final four digits of Phillips' Social Security number, his correct date of birth and a prior address matching one once attached to Gregg Allen Phillips. He has lived in all three states.

At the time of November's presidential election, Phillips' status was "inactive" in Mississippi and suspended in Texas. Officials in both states told the AP that Phillips could have voted, however, by producing identification and updating his address at the polls.

Citing concerns about voters registered in several states, the president last week called for a major investigation into his claim of voter fraud, despite his campaign lawyer's conclusion that the 2016 election was "not tainted."

"When you look at the people that are registered, dead, illegal and two states, and some cases maybe three states, we have a lot to look into," Trump said in an ABC interview.

Reached by telephone Monday, Phillips said he was unaware of his multiple registrations but asked, "Why would I know or care?"

"Doesn't that just demonstrate how broken the system is?" he asked. "That is not fraud — that is a broken system. We need a national ID that travels with people."

Phillips has been in the national spotlight since Nov. 11, when he tweeted without evidence that his completed analysis of voter registrations concluded the "number of non-citizen votes exceeded 3 million."

Thousands of people liked and retweeted the claim, which led to a viral article three days later on InfoWars.com, a site known to traffic in conspiracy theories.

Phillips also has previously tweeted about the dangers of "inactive voters" being able to vote in U.S. elections. "There is already law that compels states to remove inactive voters. Many don't," Phillips tweeted Nov. 29.

According to media reports, five Trump family members or top administration officials also were registered to vote in two states during the 2016 election — chief White House strategist Stephen Bannon; Press Secretary Sean Spicer; Treasury Secretary nominee Steven Mnuchin; Tiffany Trump, the president's youngest daughter; and Jared Kushner, Trump's son-in-law and a senior White House adviser.

The Houston-based True the Vote has challenged the validity of voter rolls in numerous states. On Friday, Phillips tweeted that the conservative group "will lead the analysis" of widespread voter fraud, and suggested in a CNN interview that it might release the underlying data in a few months.

Shortly after Phillips appeared on CNN on Friday, Trump tweeted: "Look forward to seeing the final results of VoteStand. Gregg Phillips and crew say at least 3,000,000 votes were illegal. We must do better!"