When Chesa Boudin is sworn in as San Francisco’s new district attorney, he said, he will immediately get to work reforming the city’s criminal justice system. Some goals, like ending mass incarceration, will take time. But others, like doing away with gang enhancements and ending money bail, will begin on day one, he said.

But as he lays out his progressive vision, Boudin will have to contend with the city’s many challenges, like open-air drug dealing, high property crime and other street-level problems. He will also need to work on relationships with people who fought against his election, like the mayor and the police union.

Boudin, a former San Francisco deputy public defender, joins a growing number of progressive candidates around the country to win election as district attorney. He must now figure out how to balance his campaign promises of reform with the realities of being one of the city’s top law enforcement officials.

“There is a lot of work to be done,” Boudin said in an interview Sunday. “I look forward to working with all the stakeholders in city government and in our community to transform the criminal justice system and make the city safer.”

When his first day will be remains fuzzy. Mayor London Breed appointed Suzy Loftus as interim district attorney one month before the election, when George Gascón quit to run for the same job in Los Angeles.

Boudin’s term doesn’t officially begin until Jan. 1, so it’s unclear whether Loftus will stick around until her term expires or whether Breed will tap the voters’ choice to take over. In a statement Sunday, the mayor’s office said it will work with Boudin and Loftus “to ensure a smooth transition that works best for the district attorney’s office and the city.”

Boudin said he didn’t know when his first official day will be, but he will use any time in between to begin building his team.

He said he’s reached out to several people about positions in the office after winning by a narrow margin Saturday, but is waiting to disclose names. One name he did mention was Gascón’s former chief of staff, Cristine Soto DeBerry, whom he asked to stay on in a leadership role in the office.

Politically, Boudin and Gascón share many similarities. Last year, Gascón began seeking alternatives to money bail after a state appeals court found the practice unconstitutional.

Boudin, who worked on the case and has been a statewide leader in ending cash bail, said that as district attorney he will either ask that defendants be released pretrial on certain conditions, like ankle monitoring, or if they are deemed too dangerous, ask a judge to hold them without bail.

He also said he will divert first-time, non-injury cases of driving under the influence to free up the courts from a large number of misdemeanor cases going to trial at the Hall of Justice. Gascón started a similar program weeks before leaving office, but Loftus pulled the plug on it days into her appointment.

Many of Boudin’s policies, though, are even more progressive than those of Gascón, who was one of the country’s most liberal district attorneys. One departure, Boudin said, is he will no longer charge gang enhancements, which greatly increase the penalty for crimes if a defendant is found to have participated in a street gang. The law has faced criticism over the disproportionate number of black and brown people who are charged with gang crimes. A 2016 audit of the state’s gang database found that only 8% of documented gang members are white.

Gang enhancements are “part of the system that’s explicitly racist,” Boudin said. “They take a huge amount of resources away from law enforcement. In the cases where we see serious conduct, we can already impose serious punishments without using racially motivated gang enhancements.”

The move will certainly frustrate the San Francisco Police Officers Association, which called Boudin the “#1 choice of criminals and gang members” in the more than $600,000 worth of attack ads it ran before the election.

Upon Boudin’s victory Saturday, police union President Tony Montoya released a statement saying, “Unfortunately, the election results mean that San Francisco residents will have to suffer through another four years of George Gascón style policies that have plagued our city and decimated public safety.”

Montoya added, “We sincerely hope the new District Attorney reconsiders his position to not contest the early release of violent felons and that he will grow into a champion of all crime victims.”

Boudin said that even after the union’s efforts to derail his campaign, he plans to “find common ground” and work closely with the police.

“I’m not a vindictive person, and I don’t hold a grudge,” he said. “There’s a lot of work to be done to rebuild the relationship between POA leadership and the communities of San Francisco. We see that in the protests and in the distrust that many jurors have with police. At the same time, we all know how much we depend on police to respond to emergencies and deal with unpredictable and dangerous situations.”

The other relationship that will need attention is with the mayor’s office. Breed and Gascón developed a testy rapport over the years, and before her controversial appointment of Loftus, the mayor said she needed someone in the office she can “work with” to accomplish her agenda.

Boudin acknowledged the mayor’s “critical role” in the city, but said, “I also think the independence that I bring is going to be critical to the interaction between the different branches.”

He also recognized the district attorney’s role in addressing street-level problems and property crime, which have been top priorities for the mayor. Some cases, he said, may require intervention by the criminal justice system, while others should be addressed “through the public health lens.”

Even with the array of policies he will start rolling out once in office, Boudin said, “I plan to do a lot of listening and planning.

“I’m open to learning from everyone who has a different perspective than I do, whether that’s in the community or at the Hall of Justice,” he said.

Evan Sernoffsky is a San Francisco Chronicle staff writer. Email: esernoffsky@sfchronicle.com Twitter: @EvanSernoffsky