Mere days after presumptive Democratic presidential nominee Joe Biden announced Sen. Kamala Harris (D-California) as his running mate, President Donald Trump encouraged speculation that Harris, a black and Asian woman born in Oakland, California, may not be a U.S. citizen.

“I heard it today that she [Harris] doesn’t meet the requirements,” Trump said on Thursday during a press conference. “I would have assumed the Democrats would have checked that out before she gets chosen to run for vice president. … They’re saying that she doesn’t qualify because she wasn’t born in this country?”

This move harkens back to when Trump questioned the citizenships of former President Barack Obama in 2011 and Sen. Ted Cruz in 2016. Cruz was born in Canada and has a Cuban-born father, while Obama was born in Hawaii, though Trump suggested that he may have been born in Kenya. It was not until 2016 that Trump admitted that Obama was, indeed, a citizen, though he still did not apologize for stoking false rumors.

From his comments, Trump seemed to be referencing a Newsweek opinion article by John Eastman, a law professor who previously ran for the position of California attorney general in the same year Kamala Harris won.

Eastman’s argument is that Harris is “ineligible for the office of vice president” due to the Citizenship Clause of the U.S. Constitution’s 14th Amendment. The 14th Amendment states: “All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.”

The issue that Eastman takes is jurisdiction, questioning if Harris’ immigrant and later naturalized parents were not under the jurisdiction of the U.S. at the time of her birth. However, the Supreme Court has held that anybody born in the United States is a citizen, and this has been true since the 1890s.

As Eastman himself acknowledged in his op-ed, many of his colleagues and other experts on the Constitution disagree with him.

Jessica Levinson, a Loyola Law School professor, told AP News, “Let’s just be honest about what it is: It’s just a racist trope we trot out when we have a candidate of color whose parents were not citizens.”