In the race to be the next chairman of the Democratic National Committee, New York City Mayor Bill de Blasio is throwing his support behind Minnesota Rep. Keith Ellison, whose frontrunner status may soon be challenged by the potential entry into the race of Labor Sec. Tom Perez.

"The Democratic Party stands at a crossroads, and needs leadership that will expand our vision to more Americans -- while also intensifying our commitment to our core values. Keith Ellison is that leader," de Blasio said in a statement provided to NBC News.

The mayor of the country’s largest city has positioned himself as a national progressive leader and is the latest in a long list of liberals supporting Ellison. But de Blasio also has longstanding ties to Hillary Clinton, whose 2000 Senate campaign he managed and whom he backed in the Democratic presidential primary.

In his endorsement, de Blasio called Ellison “a unifier who worked tirelessly for both Bernie Sanders and then Hillary Clinton, he will bring the party and the grassroots together while broadening and deepening the Democratic Party's connections to the American people.”

And the mayor praised Ellison as a “grassroots organizer,” who “has delivered real results like voter turnout in his native Minnesota,” while also being a “passionate fighter for economic fairness.”

Ellison, who supported Sanders in the primary, is trying to avoid turning the DNC leadership race into a rehash of the heated presidential primary.

President Obama and others have encouraged Perez, who backed Clinton, to run in part because of concern that Ellison may too narrowly represent the Sanders wing of the party, even though the Minnesota congressman has received endorsements from several major mainstream figures like Senate Minority Leader Chuck Schumer and former Clinton allies like the American Federation of Teachers union.

With Perez expected to declare his run this week with a strong showing of support, de Blasio’s declaration also comes at a time when Ellison is trying to demonstrate his own momentum.

The field of candidates in the DNC Chair race, which will be decided in February, also includes New Hampshire Democratic Party Chair Ray Buckley and South Carolina Democratic Party Chair Jaime Harrison.