Cory Booker sent the message loud and clear.

“Kamala Harris doesn’t have sh-t to prove,” the U.S. senator from New Jersey tweeted on Saturday evening.

Booker, 50, posted the tweet in reply to a New York Times story about a tweet that Donald Trump Jr. shared during the Democratic debate this week.

“Kamala Harris is implying she is descended from American Black Slaves,” right-wing personality Ali Alexander had posted. “She’s not. She comes from Jamaican Slave Owners. That’s fine. She’s not an American Black. Period.” In Alexander’s Twitter bio, he claims to have “exposed” Harris and uses the hashtag #NeverKamala.

Trump Jr., 41, shared Alexander’s tweet, adding “Is this true? Wow” during Thursday’s debate. He later deleted the tweet.

“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,” Trump Jr.'s spokesman, Andy Surabian, told the Times. “And once he saw that folks were misconstruing the intent of his tweet, he quickly deleted it.”

Harris, 54, a senator from California running against Booker for the Democratic nomination for president, was born in Oakland, California. Her parents came to the U.S. from India and Jamaica.

Other Democratic candidates for president, including Elizabeth Warren, 70, defended Harris on social media.

“The attacks against @KamalaHarris are racist and ugly," tweeted the senator from Massachusetts. “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."

The attacks against @KamalaHarris are racist and ugly. 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. — Elizabeth Warren (@ewarren) June 29, 2019

“The same forces of hatred rooted in ‘birtherism’ that questioned @BarackObama’s American citizenship, and even his racial identity, are now being used against Senator @KamalaHarris," tweeted former Vice President Joe Biden, 76. “It’s disgusting and we have to call it out when we see it. Racism has no place in America.”

President Donald Trump built his support for a presidential run by endorsing a birtherist conspiracy claiming that President Barack Obama was not born in the United States, leading calls for the president to produce his birth certificate. In 2011, the White House released Obama’s birth certificate, showing that he was born in Honolulu, Hawaii. In September 2016, less than two months before the presidential election, Trump admitted that Obama was, in fact, born in the U.S.

“The presidential competitive field is stronger because Kamala Harris has been powerfully voicing her Black American experience,” tweeted Pete Buttigieg, 37, Democratic candidate and mayor of South Bend, Indiana. “Her first-generation story embodies the American dream. It’s long past time to end these racist, birther-style attacks.”

Buttigieg’s fellow candiate and former Texas Rep. Beto O’Rourke, 46, also condemned the Alexander tweet on Saturday.

The same forces of hatred rooted in 'birtherism' that questioned @BarackObama's American citizenship, and even his racial identity, are now being used against Senator @KamalaHarris. It’s disgusting and we have to call it out when we see it. Racism has no place in America. — Joe Biden (@JoeBiden) June 29, 2019

“There’s a long history of black Americans being told they don’t belong—and millions are kept down and shut out to this day,” he tweeted. “@KamalaHarris is an American. Period. And all of us must call out attempts to question her identity for what they are: racist.”

Another candidate, Sen. Amy Klobuchar of Minnesota, 59, rallied to defend Harris.

“These troll-fueled racist attacks on Senator @KamalaHarris are unacceptable,” she tweeted. “We are better than this (Russia is not) and stand united against this type of vile behavior.”

The coordinated smear campaign on Senator @KamalaHarris is racist and vile. The Trump family is peddling birtherism again and it’s incumbent on all of us to speak out against it. — Jay Inslee (@JayInslee) June 29, 2019

Washington Gov. Jay Inslee, 68, also linked the tweet Trump Jr. shared to birtherism.

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

A standout moment from Thursday’s debate was when Harris took Biden to task for his comments on working with segregationist senators and his past stance on federal intervention in busing to integrate schools.

At a fundraiser, Biden had called collaborating with segregationist senators James Eastland of Mississippi and Henry Talmadge of Georgia in the 1970s an example of of bygone “civility” in politics.

These troll-fueled racist attacks on Senator @KamalaHarris are unacceptable. We are better than this (Russia is not) and stand united against this type of vile behavior. — Amy Klobuchar (@amyklobuchar) June 29, 2019

“I was in a caucus with James O. Eastland,” Biden said at the event. “He never called me ‘boy,’ he always called me ‘son.’"

Booker said Biden’s reference to “boy” was hurtful, given the history of how the term has been used to disparage black men, and asked for an apology for his comments about the segregationist lawmakers.

“You don’t joke about calling black men ‘boys,'" the senator said in a statement.

Harris addressed Biden’s comments on the debate stage Thursday.

“I do not believe you are a racist,” she told him. “And I agree with you when you commit yourself to the importance of finding common ground. But I also believe — and it’s personal, it was 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."

Sen. Kamala Harris sparred with former Vice President Joe Biden (pictured with Sen. Bernie Sanders) at the second night of the Democratic debate in Miami Thursday night.Drew Angerer | Getty Images

“It was not only that, but you also worked with them to oppose busing,” Harris said. She was referring to the former vice president’s historical position that the federal government should not get involved in busing students in order to desegregate schools.

“And there was a little girl in California who was part of the second class to integrate her public schools, and she was bussed to school every day," Harris continued. “And that little girl was me.”

Biden responded by calling Harris’ comments “a mischaracterization of my position across the board.”

“I do not praise racists," he said.

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. https://t.co/x5Wdx8DKr8 — Pete Buttigieg (@PeteButtigieg) June 29, 2019

Harris stayed on the issue of busing.

“But Vice President Biden, do you agree today that you were wrong to oppose busing in America then? Do you agree?”

“I did not oppose busing in America,” Biden replied. “What I opposed is busing ordered by the Department of Education.”

Harris said that nearly two decades after Brown v. Board of Education, she was part of the second class to integrate Berkeley, California public schools.

"That’s where the federal government must step in,” she said. “That’s why we have the Voting Rights Act and the Civil Rights Act. That’s why we need to pass the Equality Act — that’s why we need to pass the ERA, because there are moments in history where states fail to preserve the civil rights of all people.”

Booker did not share a debate stage with Harris because he was part of the first group of 10 Democrats to debate on Wednesday, alongside candidates including Warren and O’Rourke. At 10 minutes and 58 seconds, he spoke the most out of all contenders that night. Booker also managed to become a Twitter meme for his reaction to O’Rourke speaking Spanish early in the debate.

There's a long history of black Americans being told they don't belong—and millions are kept down and shut out to this day. @KamalaHarris is an American. Period. And all of us must call out attempts to question her identity for what they are: racist. https://t.co/g3n7lmoU2h — Beto O'Rourke (@BetoORourke) June 29, 2019

Have a tip? Amy Kuperinsky may be reached at akuperinsky@njadvancemedia.com. Follow her on Twitter @AmyKup or on Facebook.

Get the latest updates right in your inbox. Subscribe to NJ.com’s newsletters.