Over the past 16 years, Lt. John Delmonico has earned a reputation as a hard-nosed negotiator and relentless defender of officers’ actions as head of the Minneapolis police union.

Now Delmonico finds himself in a tough fight for re-election after his longtime second-in-command announced that he’s running for the top leadership job, setting off a fierce behind-the-scenes battle for the allegiance of the city’s rank-and-file police officers.

Lt. Bob Kroll, who was named union vice president in 2006, said he plans to run in this month’s election and has already secured support of a former union chief.

“Kroll has done a great job in being the lead guy in discipline,” former union president Al Berryman said on Tuesday.

Berryman said Delmonico has reached the same pivotal point he did years ago.

“You need to let somebody with new ideas and new thoughts to come in,” he said. “You don’t have much energy after 16 years.”

In an e-mailed response to the Star Tribune, Kroll said that he and Delmonico have different visions for the future of the union, but declined to comment further.

Union leadership fights can be brutal, but rarely spill out into the public. Mayor Betsy Hodges and Police Chief Janeé Harteau either were not available or declined to comment.

Delmonico has been mostly unchallenged since taking over the union from Berryman in 1999. The union represents the city’s 850 rank-and-file police and park police officers, and is a powerful force in City Hall and sometimes even at the State Capitol.

The job, which pays about $29,000 a year, requires a rock-ribbed defense of officer conduct and a willingness to clash with the police chief and the mayor. It can be a delicate balancing act while also trying to hold the support of the officers they represent.

Delmonico said he was surprised by Kroll’s decision to run, but knows challenges are part of the job.

“I believe in the democratic process,” Delmonico said. “If somebody said they think they can do my job better than I can, it’s up to the members to speak up and decide who runs the federation.”

Last fall, an online uproar developed over comments the 27-year department veteran made questioning Hodges’ support of the city’s officers in a KSTP-TV report that suggested the mayor flashed a gang sign in a picture with a black resident who had a criminal past. The incident and the uproar became a nationwide sensation, dubbed #pointer­gate. Delmonico and the mayor have said previously that they have moved on from the incident.

Privately, some police officers say Kroll, who regularly represents cops in disciplinary hearings, is more attuned to the wants of the rank-and-file.

Delmonico’s supporters, however, point to his repeal of the residency requirement for the city’s cops and commitment to increasing diversity within the department.

The department’s black officers, in particular, benefited from Delmonico’s efforts to work on their behalf when they were passed over for promotions, Sgt. Charles Adams said.

“We’ve never had a president of a federation sit down with the black community like that,” said Adams, a longtime homicide detective. “He always asks people, ‘What do you think?’ He’s not the type of leader to say, ‘I’m the leader, this is what we’re going to do.’ And I don’t know if you’re going to get that from the other guy.”

Delmonico said his style is less combative.

“I literally could be in the news every day, fighting with the chief and the mayor about something, but I have to ask myself, ‘What is my mission?’ ” Delmonico said. “When something happens with the police, there are always different angles: There’s the administrative side, there’s the political side, there’s the community side and there’s the cop side.”

Kroll has had a spotty past with the department over the years.

He has been accused in lawsuits of brutality and has been the focus of several internal probes, including one that led to his demotion.

Kroll was overheard calling then newly-elected Rep. Keith Ellison, a DFLer who is Muslim and black, a terrorist, according to a racial discrimination lawsuit filed by five black officers, known collectively as the “Mill City 5.”

The officers, including current deputy chief Medaria Arradondo, said the episode was symptomatic of the tolerance the police department had “for racially discriminatory conduct by white officers.”

At the time, Kroll denied calling Ellison a terrorist or even mentioning him by name at a police ethics class where colleagues say the remarks were overheard.

Then-Chief Tim Dolan issued a public apology to Ellison and called Kroll’s comments unacceptable.

Ballots for the election are being mailed out April 15. The results will be announced on April 30.