Incumbents in San Francisco who don’t face term limits tend to sail to re-election every four years, holding their position as long as they want.

That won’t be the case for District Attorney George Gascón, who more than a year before facing re-election in November 2019 has a very formidable opponent.

Suzy Loftus, assistant chief legal counsel in the Sheriff’s Department and the former president of the city’s Police Commission, will file papers Tuesday to challenge Gascón. She’s running on the platform that San Franciscans are tired of car break-ins, home break-ins, blatant crime on their sidewalks and a criminal justice system that seems to merely point fingers in response.

In yet one more example of San Francisco being like nowhere else, several moderate district attorneys in counties around California staved off June challenges from the left that were funded by deep pocketed liberals, including billionaire George Soros.

But Gascón — one of the most progressive district attorneys in San Francisco history and a chief backer of Proposition 47, which reduced some nonviolent crimes from felonies to misdemeanors — now faces a somewhat more moderate challenger in Loftus. And yes, Soros will apparently hold two fundraisers for Gascón.

It’s a far different picture than in 2015, when Gascón ran unopposed.

Loftus will have some impressive company at 1 p.m. Tuesday when she is scheduled to formally enter the race at the Department of Elections in City Hall. Mayor London Breed, who was joined by Loftus’ daughters when she filed her own paperwork to run for mayor, will return the favor.

Also endorsing Loftus are Supervisors Malia Cohen, Katy Tang, Catherine Stefani and Vallie Brown; Oakland Mayor Libby Schaaf; state Sen. Scott Wiener; and BART board members Lateefah Simon and Bevan Dufty.

Loftus, 44, has some credentials Gascón just can’t beat. In the Year (or Years?) of the Woman, her gender and deep wellspring of female support could be a plus.

She’s also a San Francisco native with deep connections throughout the city and particularly on the more moderate west side, where she lives in the Outer Sunset with her husband, Tom Loftus, who works for San Francisco Government TV, their three daughters and her mother.

And most central to the question of who should be San Francisco’s top prosecutor is the fact that Loftus has prosecuted hundreds of criminal cases throughout her career. Gascón, famously, had not prosecuted a single criminal case when then-Mayor Gavin Newsom in January 2011 moved him from chief of police to fill the seat of District Attorney Kamala Harris after she was elected California’s attorney general.

Loftus worked as a prosecutor in the district attorney’s office under Harris and worked for her in the attorney general’s office, too. When Harris won a seat in the U.S. Senate and left for Washington, Loftus moved to the Sheriff’s Department.

She had to leave her seat on the Police Commission to take that job and said seeing the city’s criminal justice system through the eyes of a regular resident was eye-opening.

“I was able to look around and see that what was happening on the street was not OK, and there are a lot of things we can do differently,” she said. “The current approach isn’t working.”

San Franciscans may wonder what that approach is, since it’s not obvious to many everyday residents. Too often, police officers say they make arrests, but the district attorney won’t prosecute. And the district attorney says he prosecutes, but the judges let repeat offenders off the hook. And the judges? Well, they don’t say much of anything at all.

Loftus said the phrase “criminal justice system” isn’t even accurate in San Francisco.

“The word ‘system’ presumes everybody is working together and working well and that there’s collaboration,” she said. “I’ve worked in enough of these different agencies to see we have a lot of work to do.”

Breed said she has worked with Loftus for about 15 years and has been impressed with her clear communication style, realistic point of view and compassion. She said she agrees “100 percent” with Loftus’ assessment of a broken, noncommunicative criminal justice system.

“She’s completely right,” the mayor said. “Everyone points the finger about whose fault it is rather than getting to the bottom of the situation.”

Loftus said that as district attorney, she would appoint neighborhood prosecutors to get to know small-business owners, residents and local police officers so they could build strong cases together and ensure there are consequences. That may also include organizing those parties to show up in court or write letters so the judge understands the significance of the crime.

“When you, as a prosecutor, feel like the voice of the community is not being heard, it’s your job to amplify it and make sure the judge knows what’s at stake,” Loftus said. “I think if that’s done consistently, we’ll get results.”

Gascón declined to comment for this column. But sources close to him say Loftus’ accusations just aren’t accurate or don’t paint the whole picture.

For example, property crime is a big problem, but violent crime is down, partly because robberies to steal smartphones from people have dropped. Gascón’s supporters argue that can be attributed to his successful push for a state law requiring smartphone kill switches, which render a phone useless if it’s stolen.

Also, the district attorney’s backers say, the Police Department’s dreadful arrest rate of 1.6 percent in car break-ins can’t be blamed on Gascón but is part of the slowdown in arrests that occurred while Loftus was on the Police Commission.

Gascón’s backers also say finger-pointing between the Police Department and district attorney’s office was at its worst when Loftus was the head of the Police Commission and has improved dramatically in the past year. Reports of car break-ins are down, and Gascón prosecutes 85 percent of those cases that do make it to his office.

The district attorney also has some impressive early endorsers, including Lt. Gov Gavin Newsom, former Supervisor Matt Gonzalez, Assessor-Recorder Carmen Chu, Assemblyman Phil Ting and Supervisors Ahsha Safai, Hillary Ronen, Norman Yee, Sandra Fewer and Aaron Peskin.

Gascón and Loftus have two other competitors, as well: Joe Alioto Veronese, another former Police Commissioner, and Leif Dautch, a California deputy attorney general, are also running.

San Francisco Chronicle columnist Heather Knight appears Sundays and Tuesdays. Email: hknight@sfchronicle.com Twitter: @hknightsf