2020 Democratic presidential candidate Julian Castro slammed Donald Trump Jr. on Sunday for questioning fellow Democratic hopeful Kamala Harris’ racial heritage, calling the president’s son a “coward” and saying his tweet last week was “disgusting.”

Trump Jr. retweeted a post last Thursday by controversial conservative personality Ali Alexander that claimed that Harris, a senator from California, “comes from Jamaican Slave Owners” but is “not an American Black.” The president’s son quickly deleted the post.

HARRIS CAPITALIZES ON DEBATE PERFORMANCE

“You notice what he did, he tweeted it out and then he deleted it, like a coward, so he could say, ‘That was just a mistake,’ but he knows what he’s doing,” Castro said during an appearance on CNN’s “State of the Union.” “He’s giving voice to these racists, you know, utterances about Sen. Harris.”

Castro added: “We need to dispel them immediately and condemn them and then not give them any more life because they’re disgusting.”

Both Castro and Harris were seen as having breakout performances during the first round of Democratic debates last week, with Harris drawing attention for slamming former Vice President Joe Biden for recently defending having worked with segregationists in the Senate and for once opposing mandatory busing of students to desegregated public schools.

Harris said Friday that the back-and-forth with Biden was her "just speaking truth." She told CBS that she has a "great deal of respect" for Biden and would make no judgment on whether his response was disqualifying.

"That's a decision for the voters to make," Harris said.

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Harris came out the big winner from last week’s debates with her campaign raising $2 million in the 24 hours after she left the stage Thursday night.

Figures provided by the California senator's campaign indicate that over half of the contributions came from people who had never given to her before.

The Associated Press contributed to this report.