United States President Donald Trump on Thursday promoted a conspiracy theory regarding Democratic vice president candidate Kamala Harris’ legitimacy to run for the post, reported The Washington Post. He raised doubts about Harris’ citizenship and thus questioned her eligibility. Harris is the first woman of colour to serve as running mate on a major party ticket.

The conspiracy theory started doing the rounds after a conservative law professor questioned Harris’ eligibility. However, US records show that Harris was born in Oakland, California, on October 20, 1964.

“I just heard it today that she doesn’t meet the requirements and by the way the lawyer that wrote that piece is a very highly qualified, very talented lawyer,” Trump claimed at a press conference. “I have no idea if that’s right. I would have assumed the Democrats would have checked that out before she gets chosen to run for vice-president.”

John Eastman, a law professor at Chapman University in California first espoused the theory in an opinion piece published in Newsweek magazine. He based his argument that Harris may not have been subject to US jurisdiction if her parents were on student visas at the time of her birth. Harris’ mother, Shyamala Gopalan, was born in India and came to the US to get a PhD in nutrition and endocrinology at the University of California at Berkeley. Her father, Donald Harris, came from Jamaica in 1963 to earn a PhD in economics from the same university.

Incidentally, Eastman was the Republican candidate for California attorney general in 2010. He lost to Steve Cooley, who later went on to be defeated by Harris in the general election.

Earlier on Thursday, Trump campaign legal adviser Jenna Ellis reposted a tweet from Tim Fitton, the head of conservative group Judicial Watch. In the tweet, Fitton questioned if Harris was “ineligible to be Vice President under the US Constitution’s ‘Citizenship Clause’”. Fitton shared the opinion piece by Eastman. “It’s an open question, and one I think Harris should answer so the American people know for sure she is eligible,” Ellis told ABC News.

Critics decry the theory as racist.

Lawyers said the conspiracy was false and Harris is eligible to be president under the constitutional requirements, reported AFP. “Lets just be honest about what it is: It’s just a racist trope we trot out when we have a candidate of colour whose parents were not citizens,” said Jessica Levinson, a professor at Loyola Law School.

Trump had used a similar “birther theory” against former President Barack Obama. For years, he claimed that Obama was not born in the US but in Kenya. Even after Obama submitted a copy of his birth certificate that showed his birthplace as Hawaii, Trump alleged it was a fake. During his 2016 election campaign, Trump finally dropped his claims.