Democratic National Committee (DNC) Chairman Tom Perez Thomas Edward PerezClinton’s top five vice presidential picks Government social programs: Triumph of hope over evidence Labor’s 'wasteful spending and mismanagement” at Workers’ Comp MORE's endorsement of New York Gov. Andrew Cuomo has created a fissure with his deputy, Rep. Keith Ellison Keith Maurice EllisonOfficers in George Floyd's death appear in court, motion for separate trials Ex-Minneapolis officer involved in Floyd death asks judge to dismiss murder charge Over 50 current, former law enforcement professionals sign letter urging Congress to decriminalize marijuana MORE (D-Minn.), who learned of the party leader's decision to get involved in the race only after a public announcement.

In a statement, Ellison said the DNC should not get involved in primary fights such as the one in New York, where Cuomo is facing a spirited challenge from the left from actress-activist Cynthia Nixon.

"The Democratic Party should not intervene in the primary process," Ellison said Thursday following Cuomo's endorsement, according to Politico. "It is our role to be fair to all contestants and let the voters decide."

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Perez defeated Ellison in a contested race last year for the party chairmanship that shined a spotlight on the divisions within the party between more centrist and liberal lawmakers.

Perez's endorsement broke from his repeated pledge not to pick favorites in the party's primary races.

Ellison was reportedly not told ahead of time that Perez would make the endorsement, a source told Politico.

"You've been delivering results and you've been delivering results that have made people's lives better. That's why Andrew Cuomo and Kathy Hochul are charter members of the accomplishments wing of the Democratic Party, and that's why I'm proud to endorse them," Perez said of Cuomo and his lieutenant governor at the New York state Democratic Convention at Hofstra University on Thursday.

A spokesman for Nixon dismissed the endorsement, telling Politico that Perez's support "won't hide the fact that [Cuomo has] effectively governed as a Republican for eight years.”

A party spokesman told NBC News that the DNC will not give any financial support to Cuomo's reelection bid during the primary.

--Updated on May 25.