Washington (CNN) Sen. Kamala Harris pushed back Saturday against online attacks about her race, comparing the latest jabs to racism faced by former President Barack Obama, as fellow 2020 candidates rallied to her defense.

During Thursday's Democratic presidential debate, Donald Trump Jr. retweeted to his millions of followers a Harris critic who took issue with her identity.

"Kamala Harris is *not* an American Black. She is half Indian and half Jamaican," the critic, who identified as African American wrote . "I'm so sick of people robbing American Blacks (like myself) of our history. It's disgusting. Now using it for debate time at #DemDebate2? These are my people not her people. Freaking disgusting."

Trump Jr. shared the tweet with the comment, "Is this true? Wow." He has since deleted the tweet and a spokesman for President Donald Trump's son told the New York Times that it was a misunderstanding.

"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," spokesman Andy Surabian told the Times . "And once he saw that folks were misconstruing the intent of his tweet, he quickly deleted it."

Lily Adams, the campaign communications director for Harris, dismissed the attack, explaining that people, including President Trump, used similar rhetoric to question Obama's birthplace . Obama was born in Hawaii.

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

Harris shined Thursday night when she took former Vice President Joe Biden to task for trying to prevent the Department of Education's efforts to enforce school busing to integrate schools during the 1970s.

"Vice President Biden, I do not believe you are a racist, and I agree with you, when you commit yourself to the importance of finding common ground," Harris said. "But I also believe -- and it's personal -- it was actually hurtful to hear you talk about the reputations of two United States senators who built their reputations and career on the segregation of race in this country."

Harris then invoked her own experience to make the point on the debate stage.

"That little girl was me," Harris said with emotion swelling in her voice. "So I will tell you that on this subject, it cannot be an intellectual debate among Democrats. We have to take it seriously. We have to act swiftly."

Biden defended Harris on Saturday, saying in a tweet that "racism has no place in America."

"The same forces of hatred rooted in 'birtherism' that questioned @BarackObama's American citizenship, even his racial identity, are now being used against Senator @KamalaHarris," Biden said. "It's disgusting and we have to call it out when we see it."

Harris, who was born in the US to an Indian mother and a Jamaican father who were both immigrants, has directly confronted critics before who have questioned her black heritage, her record incarcerating minorities as a prosecutor and her decision to marry a white man.

In an interview with The Breakfast Club hosts DJ Envy and Charlamagne Tha God that aired in March, the show's hosts asked the California Democrat to address a series of derogatory memes that have circulated on social media. One of the hosts cited a meme that said Harris is "not African-American" because her parents were immigrants and she spent her high school years in Canada.

"So I was born in Oakland, and raised in the United States except for the years that I was in high school in Montreal, Canada," Harris responded with a laugh. "And look, this is the same thing they did to Barack (Obama). This is not new to us and so I think that we know what they are trying to do."

"They are trying to do what has been happening over the last two years, which is powerful voices trying to sow hate and division, and so we need to recognize when we're being played," Harris said.

Of the 2020 Democratic hopefuls, Massachusetts Sen. Elizabeth Warren appeared to be the first on Saturday to defend Harris.

"The attacks against @KamalaHarris are racist and ugly," Warren tweeted. "We all have an obligation to speak out and say so. And it's within the power and obligation of tech companies to stop these vile lies dead in their tracks."

A Twitter spokesperson told CNN Sunday that accounts attacking Harris during Thursday's debate were not automatic "bots," saying, "We saw no coordinated use of automation during recent debates."

Other Democrats on the campaign trail chimed in to defend Harris.

Washington Gov. Jay Inslee accused the Trump family of "peddling birtherism," an apparent reference to the president's attacks against Obama.

"The coordinated smear campaign on Senator @KamalaHarris is racist and vile, Inslee tweeted. "The Trump family is peddling birtherism again and it's incumbent on all of us to speak out against it."

Former Texas Rep. Beto O'Rourke pointed to the "long history of black Americans being told they don't belong—and millions are kept down and shut out to this day."

Calling for a unified commitment to combating racist rhetoric, O'Rourke added, Harris "is an American. Period. And all of us must call out attempts to question her identity for what they are: racist."

Mayor of South Bend, Indiana, Pete Buttigieg joined the chorus of 2020 supporters, saying it was time to end these attacks.

"The presidential competitive field is stronger because Kamala Harris has been powerfully voicing her Black American experience. Her first-generation story embodies the American dream. It's long past time to end these racist, birther-style attacks," Buttigieg said.

New Jersey Sen. Cory Booker decided to use blunt language in his Harris defense.

".@KamalaHarris doesn't have sh** to prove," he tweeted

Democratic presidential hopeful Julián Castro weighed in on the discussion Sunday, calling the online racist attacks "disgusting" and saying "it has not place in our politics."

"This is the game that these folks play. They put something out there, you notice what he did, he tweeted it out and then he deleted it. Like a coward so he could say, 'Oh, that was just a mistake.' But he knows what he's doing," Castro said on Sunday in an interview with CNN's Brianna Keilar on "State of the Union."

"He's giving voice to these racist utterances about Senator Harris," Castro said. "We need to dispel them immediately and condemn them and then not give them any more life because they're disgusting."

Twitter confirmed to CNN that it had suspended some accounts that had been attacking Harris' race, but said that those accounts had been suspended for other rule violations.

"Our policies ban misleading, deceptive, and spammy behavior and prohibit attempts to game trends or cause unrelated Tweets to appear in search results. We've aggressively stepped up our actions in this regard," a Twitter spokesperson said in a statement. "In addition to these existing preventative systems, we will be protecting the integrity of the conversation around key topics and trends throughout the election, including during debates. We saw no coordinated use of automation during recent debates."

This story has been updated.