Donald Trump has turned birther again, suggesting the Democratic Party's nominee for vice president, Kamala Harris, might be ineligible for the job.
Joe Biden chose Harris, a serving US Senator and former prosecutor, to be his running mate earlier this week. She is the first black woman in US history to be picked for a presidential ticket.
After that decision was announced, law professor John Eastman published an article in Newsweek, claiming there were "some questions for Kamala Harris about eligibility".
"The fact that Senator Kamala Harris has just been named the vice presidential running mate for presumptive Democratic presidential nominee Joe Biden has some questioning her eligibility for the position," Professor Eastman wrote.
"The 12th Amendment provides that 'no person constitutionally ineligible to the office of president shall be eligible to that of vice president of the United States'. And Article II of the Constitution specifies that 'no person except a natural born citizen ... shall be eligible to the office of President'.
"Her father was, and is, a Jamaican national, her mother was from India, and neither was a naturalised US citizen at the time of Harris' birth in 1964.
"That, according to these commentators, makes her not a 'natural born citizen', and therefore ineligible for the office of the president and, hence, ineligible for the office of the vice president."
During today's White House media briefing, Mr Trump was asked about Prof Eastman's article.
"I just heard that. I heard it today, that she doesn't meet the requirements," Mr Trump said.
"And by the way, the lawyer that wrote that piece a very highly qualified, very talented lawyer.
"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.
"But that's a very serious – you're saying that, they're saying that she doesn't qualify because she wasn't born in this country?"
"No, she was born in this country, but her parents did not – the claims say that her parents did not receive their permanent residence at that time," a reporter told him.
"Yeah, I don't know about it, I just heard about it. I'll take a look," said the President.
There is nothing to look at.
Harris was born in Oakland, California in 1964. Legal precedent is that anyone born in the United States is a citizen, and therefore eligible to be president.
"All persons born or naturalised in the United States, and subject to the jurisdiction thereof, are citizens of the United States," the 14th Amendment to the US Constitution reads.
Nevertheless, one of Trump's campaign advisers, Jenna Ellis, told CBS News today Harris' eligibility was an "open question, and one I think Harris should answer so the American people know for sure".
CBS also spoke to constitutional law expert Erwin Chemerinsky, who is the dean of Berkeley Law School. He called it a "truly silly argument".
"Under Section 1 of the 14th Amendment, anyone born in the United States is a United States citizen. The Supreme Court has held this since the 1890s," he said.
"Kamala Harris was born in the United States."
Before he became president, Trump was one of the most prominent people pushing the racist "birther" conspiracy theory.
That theory claimed Trump's predecessor, Barack Obama, was born outside the United States, and therefore ineligible for the presidency.
Obama was born in Hawaii.
"Why doesn't he show his birth certificate?" Trump asked during an appearance on The View in 2011.
"I would like to have him show his birth certificate," he told NBC's Today Show around the same time.
"Because if he can't, if he can't, if he wasn't born in this country, which is a real possibility – then he has pulled one of the great cons in the history of politics."
Trump famously claimed he had sent investigators to Hawaii.
"You have people now, down there searching. I mean in Hawaii?" Today Show host Meredith Vieira asked him.
"Absolutely. And they cannot believe what they're finding," Trump replied.
There has never been any evidence that the investigators in question existed.
When Obama did eventually produce his long-form birth certificate in an effort to stamp out the theory, Trump claimed it was fraudulent.
He continued to promote the conspiracy theory for five years, and didn't acknowledge Mr Obama had been born in the US until his 2016 presidential campaign.
"President Barack Obama was born in the United States. Period," Trump said.
He claimed the birther theory has been started by Hillary Clinton.
In her 2018 memoir Becoming, former first lady Michelle Obama said she would "never forgive" Trump for spreading the lie about her husband.
"The whole thing was crazy and mean-spirited, of course, its underlying bigotry and xenophobia hardly concealed," she wrote.
"But it was also dangerous, deliberately meant to stir up the wingnuts and kooks. What if someone with an unstable mind loaded a gun and drove to Washington? What if that person went looking for our girls?
"Donald Trump, with his loud and reckless innuendos, was putting my family's safety at risk. And for this, I would never forgive him."