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.