Sanders made a similar announcement on CNN’s “State of the Union.”

Sen. Bernie Sanders. | Alex Wong/Getty Images

Jackson ran for president in 1984 and 1988, winning four states in 1984 and 13 in 1988, including Michigan. He was the first African American ever to win a Democratic primary.

Jackson got Sanders' support in his 1988 bid, when he faced off against Biden, among others. (Gov. Michael Dukakis of Massachusetts was the eventual nominee.) At the time, Biden told a mostly black audience to reject Jackson’s candidacy. Jackson has said that the former vice president has grown in his positions, but the primary competition would force Biden to deal with the past.

In a statement Sunday, Jackson said Sanders made several commitments to him: expanding Pell Grants, nominating African American women to the Supreme Court and his Cabinet, introducing in Congress a constitutional amendment on the right to vote, and considering an African American woman as his running mate.

"With the exception of Native Americans, African Americans are the people who are most behind socially and economically in the United States and our needs are not moderate,” Jackson said in the statement. “A people far behind cannot catch up choosing the most moderate path. The most progressive social and economic path gives us the best chance to catch up and Senator Bernie Sanders represents the most progressive path. That's why I choose to endorse him today.”

"The Biden campaign has not reached out to me or asked for my support," he added. "The Sanders campaign has, and they responded to the issues I raised."

POLITICO NEWSLETTERS 2020 Elections Unpacking the national conventions and the race for the White House. Sign Up Loading By signing up you agree to receive email newsletters or alerts from POLITICO. You can unsubscribe at any time. This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Sanders recently hired one of its surrogates, activist Phillip Agnew, to boost organizing in black communities. On Sunday, Sanders added that he has the support of every major grassroots organization because his agenda supports working people.

The same morning, Sen. Kamala Harris of California threw her support behind Biden.

“What was very clear from the media narrative and what the establishment wanted was to make sure that people coalesced around Biden and defeat me,” Sanders said on ABC. “We're taking … on the establishment.”