Donald Trump Jr., the president's eldest son and outspoken defender, fanned the flames of a racist conspiracy by sharing a tweet falsely claiming that Sen. Kamala Harris isn't a black American.

The tweet that Trump Jr. promoted suggested Harris, who was born in Oakland, California to an Indian-American mother and a Jamaican-American father, isn't black enough to be an authority on issues of race.

"Is this true? Wow," Trump Jr. tweeted during Thursday's Democratic 2020 primary debate.

Trump Jr. later deleted his tweet and Harris' campaign compared the attack to the president's years-long attempts to discredit President Barack Obama with his "birther" conspiracy.

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Donald Trump Jr., the president's eldest son and outspoken defender, fanned the flames of a racist conspiracy by sharing a tweet falsely claiming that Sen. Kamala Harris isn't a black American.

The tweet that Trump Jr. promoted suggested that Harris, who was born in Oakland, California to an Indian immigrant mother and a black Jamaican immigrant father, isn't black enough to be an authority on issues of race.

"Kamala Harris is implying she is descended from American Black Slaves," Ali Alexander, a fringe alt-right activist, tweeted. "She's not. She comes from Jamaican Slave Owners. That's fine. She's not an American Black. Period."

Trump Jr. shared Alexander's tweet with his 3.6 million followers during Thursday's Democratic 2020 primary debate, writing, "Is this true? Wow."

During Thursday's debate, Harris took a few minutes to discuss issues of race, challenging former Vice President Joe Biden on his record of opposing school desegregation through busing, and his recent controversial remarks about his work with notorious segregationist senators.

"Growing up, my sister and I had to deal with the neighbor who told us her parents couldn't play with us because she — because we were black," Harris added, at one point noting that she was the "only black person on this stage."

Alexander told the Daily Beast that he attacked Harris because she "stole debate time under the premise that she is an African-American when she is in fact a biracial Indian-Jamaican who is a first generation American."

Read more: 'Americans don't want a food fight': Kamala Harris brought the house down by bringing order to the 2020 debate stage

Trump Jr. later deleted his tweet. Harris' campaign compared the attack to the president's years-long attempts to discredit President Barack Obama with his "birther" conspiracy.

"This is the same type of racist attacks his father used to attack Barack Obama. It didn't work then and it won't work now," campaign spokeswoman Lily Adams told news outlets.

A spokesman for Trump Jr. said he erased the message after his followers "misconstrued" its intent.

"Don's tweet was simply him asking if it was true that Kamala Harris was half-Indian because it's not something he had ever heard before," Andy Surabian, Trump Jr.'s spokesperson told the New York Times, "and once he saw that folks were misconstruing the intent of his tweet, he quickly deleted it."

But, with Trump Jr.'s help, the message went viral in conservative circles online, fueling existing conspiracies about Harris' race as part of broader right-wing attempts to discredit the candidate.

"My tweet is ridiculously viral. You're welcome, America!" Alexander tweeted on Friday night. "Indian-Jamaican Kamala Harris is bad for Black Americans. #BlackHillary."