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Democratic gubernatorial candidate Jim Johnson speaks in Princeton in February.

(Aristide Economopoulos | NJ Advance Media for NJ.com)

TRENTON -- Former New York City Mayor David Dinkins has endorsed Democrat Jim Johnson to become New Jersey's next governor, Johnson's campaign announced Wednesday.

Dinkins, 89, a Trenton native who remains the only black mayor in the history of America's largest city, said in a statement that he knows "firsthand what it takes to challenge the establishment in order to make history."

"Jim Johnson not only has what it takes, he has dedicated his life to fighting for justice and bringing about change," Dinkins said.

The former mayor -- who served from 1990 to 1993 -- added that Johnson has "challenged the powerful on behalf of the people, and brought diverse communities together to solve big problems."

Johnson, a former Treasury official in President Bill Clinton's administration and a former attorney, is considered an underdog in the race to succeed Gov. Chris Christie, a term-limited Republican whose final year ends in January.

Former New York City Mayor David Dinkins waives to the crowd at the 2006 U.S. Tennis Open in New York.

The 55-year-old Montclair native and resident is one of six Democrats running for the party's nomination in the June 6 primary.

Johnson, also the former chair of the Brennan Center for Justice at New York University, is the race's only black candidate and would become New Jersey's first black governor if he wins.

The primary's front-runner is Phil Murphy, a former U.S. ambassador to Germany who has lent his campaign at least $10 million and has the support of all 21 county parties. Murphy's five rivals -- including Johnson -- trail him by double-digits in recent polls.

Dinkins, a Trenton Central High School graduate, defeated incumbent Mayor Ed Koch in the 1989 New York Democratic mayoral primary and went on to beat Republican Rudy Giuliani in the general election.

Dinkins served only one term, losing to Giuliani in a rematch in 1993.

Johnson said Dinkins has been a role model for years and that he's "humbled to receive his trust."

"Mayor Dinkins won his primary in a historic victory, and paved the way for so many of us to run for office," Johnson said in a statement.

Brent Johnson may be reached at bjohnson@njadvancemedia.com. Follow him on Twitter @johnsb01. Find NJ.com Politics on Facebook.