New York City Councilman Rory Lancman made official Wednesday his candidacy to become the next district attorney of Queens County.

Lancman's challenge to longtime incumbent District Attorney Richard Brown has been long anticipated. As the chair of the council's Justice System committee—a later iteration of a committee created after he joined the body in 2013—Lancman has made reform efforts a top priority, positioning himself as a leader on criminal justice issues.

That history is expected to serve as a foundation for Lancman, 49, to run as a progressive alternative to Brown, who was a state court judge before his long tenure as DA began in 1991.

In an early example of how Lancman seeks to contrast his approach to criminal justice to Brown's, the councilman clashed earlier this month with James Quinn, Brown's senior executive ADA, in a raucous debate before a Queens civic association over the effort to close the jail complex on Rikers Island—a plan that Brown's office has actively opposed.

For Lancman, who supports the plan to phase out Rikers and build new jail facilities in four of the five boroughs, the debate with Quinn got to the heart of why he wants to be DA.

“It just refers to this carceral philosophy that I think the public is tired of,” Lancman said in an interview. “We want a criminal justice system that isn't racist, that isn't discriminatory to the poor and that isn't gaming the system to squeeze people into pleading guilty.”

Lancman's rollout emphasized support from both local clergy members, and family members of victims of high-profile police-involved killings: Eric Garner's mother, Gwen Carr, who called Lancman the candidate who would “bring real criminal justice reform to Queens” and Sean Bell's widow Valerie Bell, who said Lancman “will not tolerate police malfeasance” as DA.

Lancman's proposals place him in the forward position of a trend of hopeful new DAs aiming to bring reform measures to the city's criminal justice system.

The line can be traced from Manhattan DA Cyrus Vance Jr.'s creation of a conviction review unit after assuming office in 2010 to the push for marijuana prosecution reforms started by Kenneth Thompson in Brooklyn and continued by his successor Eric Gonzalez.

If Lancman's reform agenda places him at the vanguard on issues such as ending a request for cash bail and promising to honor the spirit of the state's often manipulated speedy trial law, it puts him leagues away from the office policies in Queens as they currently stand.

Brown has made clear that his office intends to continue with policies critics see as better left in the dustbin of history.

For example, forming a conviction review unit like the one in Brooklyn that has taken part in two-dozen exonerations of wrongfully-convicted defendants, has been a nonstarter in Queens. Brown's office has openly resisted backing off low-level offense prosecutions, such as for turnstile jumping, while declining to join his Manhattan and Brooklyn colleagues calls for reform of marijuana prosecutions.

As a progressive-leaning candidate running for a countywide office in Queens, where 22 percent of voters cast ballots for President Donald Trump in the 2016 election, Lancman may face a challenge in winning over more conservative neighborhoods in the borough like Maspeth or Howard Beach.

To win over right-leaning voters, Lancman said, he said he will focus on the fiscal toll that mass incarceration takes on public coffers: The city comptroller reported last year that it costs $270,000 annually to house a single inmate on Rikers.

By offering Brown his first legitimate political threat almost one year before a likely primary election, Lancman puts pressure on Brown, 85, to make a call on whether he intends to seek another term.

While Lancman aims to occupy the progressive lane, some in the legal community maintain reservations about his left-leaning credentials. As one member of a local criminal justice reform organization familiar with Lancman and his work in the council noted, a skepticism remains about his ultimate intentions of running for DA.

“This progressive reform hat he's worn for a few years might just be a means to an end for him—a big office and more notoriety,” the individual, who sought anonymity so as not to damage a working relationship with the councilman, told the New York Law Journal. “Most folks are concerned he'll operate as a moderate in the office and fail to usher in needed change.”

Whether Brown chooses to run again, Lancman's announcement Wednesday seems likely to be the first of many as a crowded field of hopefuls eyes the race.

Those who have been mentioned as possibly having interest in running for the seat include Queens Borough President Melinda Katz, former Queens Supreme Court Justice Gregory Lasak, Bronx Criminal Court Judge George Grasso and local Court of Claims Judge Peter Vallone Jr.