On Jan. 17, some 200 London Breed supporters gathered at Emporium SF, an arcade and bar in the Fillmore district, for the first rally of her mayoral campaign. Breed had been acting mayor for more than a month, but now she had filed her papers to run in the June election, and she was free to make the case for why she deserved the job for good.

People “are just really fired up and ready to go for this campaign,” Breed said, borrowing a Barack Obama rally line, her voice booming through a wireless microphone.

The arcade is cavernous, drafty, majestic, lined with pinball machines. It used to be a church and, before that, a movie theater and live-music space, long a part of the historically black Fillmore’s fabric, before that fabric started to unravel. In the crowd, Mattie Scott pointed up to the balcony. “I was sitting up there with my boyfriend in 1971, watching ‘Shaft,’” she said.

Breed grew up not far from here, raised by her grandmother in public housing that was torn down in the 1970s, part of an “urban renewal” plan that displaced large swaths of San Francisco’s black community. Then gentrification picked up where urban renewal left off. Today, African Americans account for less than 6 percent of the city, and in recent years, San Francisco’s black population has continued to fall by about 5 percent annually.

Many of the people cheering her at the arcade have known Breed since she was a girl. They were her neighbors, her mentors, the ones who looked after her, who made sure she had lunch money and took the straight path to school.

“Everybody knew to take care of London,” said Eli Crawford, a Fillmore nonprofit leader. “We always felt she was special.”

Now that girl was standing before them on the theater’s stage, a giant screen displaying her campaign logo, a woman of 43 who was one of them, and could be the city’s next mayor.

“I was really fortunate,” Breed said. “My grandmother. She was like, if you want to live in this house, you gotta go to school. You gotta clean up. You gotta wash dishes and everything else. I didn’t want to do that stuff. But she made me do it. And as a result, here I am.”

From her first public appearance the morning after Mayor Ed Lee’s sudden death through her early weeks as acting mayor, Breed spoke often about her ties to this community, how it shaped her and inspired her to enter politics. Though the Board of Supervisors she heads contains only liberal members, it is split into “moderate” and “progressive” factions. Breed is among the board’s moderates, a group seen as friendlier toward developers and tech companies. But she argues those labels mean nothing — that ideology is a luxury to people who are struggling.

“We talk about ideology in San Francisco,” Breed told the crowd, her voice building to a crescendo. “I don’t care if you’re a progressive. I don’t care if you’re a moderate. I don’t care if you’re black or you’re white or you’re pink or you’re purple. I don’t care what you are. If you’re a San Franciscan, I’m … Your ... Mayor ... Too!”

It was the speech of a candidate feeling a lot of political wind in her sails. And why not? At that moment, it seemed that Breed was likely to hold onto the mayor’s seat until June, carrying the force of incumbency into the election. If she won then, she could run twice more. Ten years of Mayor London Breed seemed a serious possibility — a black woman from a poor background cementing her position in San Francisco’s power structure.

That, anyway, was how it was starting to look, before the winds changed.

Shortly after Dec. 12, when Lee died from cardiac arrest and Breed was thrust into his job, The Chronicle decided to write about London Breed by observing her as she took on this new role. A reporter began to shadow her at public events, and sometimes at private tours of city facilities. The goal was to offer a portrait of her in this moment, to show her under the spotlight, in the hopes it would reveal something about Breed and the kind of mayor she might be.

This proved difficult, for a couple of reasons. One is that Breed stepped cautiously in public, not showing all of her hand.

And then she got ousted. On Tuesday night, her tenure as acting mayor came to an abrupt end. A power-play vote by supervisors replaced Breed — the first black woman to serve as mayor of San Francisco — with a wealthy white man, Supervisor Mark Farrell.

The vote altered the dynamic of the mayor’s race, and not only because it removed Breed’s advantage as an incumbent. It also outraged her most devoted supporters. Many of them see the removal of Breed as the latest in a long line of insults, another example of how San Francisco displaces African Americans. Regardless of who and what London Breed actually is, the fact of her ouster is now a campaign issue, and may be the backdrop against which this year’s mayoral race will unfold.

In late December and early January, in numerous appearances around the city, Breed stepped from a black city sport utility vehicle in high heels and performed the sorts of duties you’d expect of an acting mayor: giving speeches at nonprofits and city facilities, reassuring residents that a steady hand was at the wheel, telling city workers their jobs matter.

She visited a short-term homeless shelter in the Dogpatch neighborhood. She toured the Auburn Hotel in SoMa, which provides 70 beds for homeless veterans, and Hummingbird Place, a new shelter catering to homeless people with mental health or addiction issues.

There were small moments of connection with strangers. On the second floor of the Auburn Hotel, a veteran named Eldon Simpson showed Breed his room. He pointed to his microwave and said that when he first moved in there was no mirror above the sink, so he shaved by looking at his reflection in the microwave.

“Gotta look pretty when you go out,” Breed said, miming a razor across her cheek.

“Well, I’m a Marine,” he replied.

At first glance, everything in this picture seemed fairly placid and friendly, a portrait of municipal normalcy, with Breed in the foreground. But at the edge of the frame, things were beginning to take a different shape.

It took only a few days after Lee’s death for some supervisors to float the idea of a caretaker mayor to replace Breed and serve until the June election. Breed, they said, was too deeply embedded in the city’s power structure. As board president, acting mayor and District Five supervisor, she had three jobs and potential conflicts. It wasn’t fair for her to carry the advantage of incumbency into the election. There should be a level playing field.

That notion raised a sticky question among Breed’s friends and supporters: What does a level playing field look like in San Francisco, exactly?

The more Breed got out into the city, the more her connections to the black community kept coming through. At a news conference for a gun buyback program in SoMa, Breed said, “I hate guns,” and explained that “I grew up in a community where gun violence was a normal thing.” She saw her first homicide when she was 12. A boy in the Fillmore named Stacy.

“He and my brother were really close,” Breed recalled later. “He was a good person. Like, everybody — all the mamas — everybody loved Stacy. And he was shot and killed.”

Standing behind Breed at the event were people she had known since she was a kid. One was Mattie Scott, a close mentor in the Fillmore and a gun control activist. Scott was holding up a photograph of her son, George, slain in 1996 in the Western Addition. He was 24, and had gone to Galileo High School with Breed. “An amazing person,” Breed said of George. “Very handsome, very charismatic. ... These are the people that we are losing because of guns.”

A few feet to Scott’s right stood Richard “Big Rich” Bougere, who grew up near Breed and teaches music to kids at the African-American Art and Cultural Complex. “She comes from the toughest housing projects in the Fillmore, period,” Bougere recalled later. “It was one way in, one way out. Nobody liked to go over there.” He used to marvel at her poise, even in high school: “When it was time to do the regular stuff, the regular teenage hood stuff, she wouldn’t entertain that. If she couldn’t lead the pack, she would be in her own pack by herself.”

Over the Christmas break, Breed visited the Art and Culture Complex, which she used to run, for a toy-wrapping party. Her friend Tyra Fennell was there. Fennell grew up in Washington, D.C., in a middle-class black family, and studied arts education at historically black Howard University, getting her master’s. Then she moved to San Francisco in 2009, taking a job at an arts organization. It was instant culture shock.

“I said to my co-worker, where are all the black people?” Fennell recalled.

For months, Fennell felt stranded. It wasn’t until someone pointed her to Breed, who started introducing her to friends and plugging her into the city, that she started to feel she had a place here. “She was really just like me,” Fennell said of Breed. “She had a real East Coast way of communicating. Straight shooter. Alpha female.”

Another day, at a neighborhood cleanup in the Sunset District, Breed noticed 19-year-old Henry Davis. His father, a minister, had baptized Breed when she was a girl, and his mother, Sheryl Davis, has long worked with Breed in the community.

“Look at you, all grown up!” Breed said to Henry, a freshman at Loyola Marymount University. Her face was lit with pride. “He’s all college and stuff,” she gushed.

“Little Henry?” Breed said later, and laughed. “Can I tell you, that kid? First of all, he’s a great singer. He is so mature. He’s such a great kid. He grew up right in our community. With all the other kids. And he’s in college. Doing well in life. Like, I’m so proud of him. I couldn’t be more proud if he had been my own son. And that really has been my work in life, because the same thing happened with me when I was growing up in the neighborhood. I had all these people … telling me what to do as a kid, when I didn’t even understand what that all meant.”

The fact that Breed was raised by a village, by people who watched out for her all the way and took pride in her progress, is an important nuance in her biography. The benchmarks are well known: raised in public housing, a brother in prison, a sister lost to a drug overdose. She grew up thinking it was normal to live in a home where the bathroom was broken, normal to brush your teeth with baking soda because there was no toothpaste. Normal for your friends to come over and see a roach and then not want to come over again. When she watched “The Cosby Show,” she said, “I was like, oh my God, a black husband and wife? And one is a doctor and one is a lawyer? I was like, awww, that can’t be.”

But she also discovered a network of teachers and pastors and political mentors who gave her a foothold in San Francisco, who helped her up and out. As an adult, Breed became an essential link in that network herself. “I wanted to elevate my status to get more resources for the community,” is how she puts it.

Breed’s district is diverse. Since 2013 she has represented the Fillmore, Cole Valley, Hayes Valley, Lower Haight and Haight-Ashbury, part of the Sunset, and Japantown. The landscape runs the gamut from million-dollar condos to housing projects; her constituents from super-wealthy to impoverished. The issues she grew up around — homelessness, affordable housing, public safety — are the city’s most urgent, she believes, affecting everyone. The case she will make to voters over the next six months is that her own fight — her struggle to prosper in an often-unforgiving city — is their fight too.

But whatever else she might mean to the city as a whole, or inside City Hall, Breed means something to a black community that has long needed to fight for its very existence here, in a city without a lot of powerful black faces. For many of those who remain, Breed is the most important ally they have.

This is why her supporters reacted with derision and anger in early January, as progressive supervisors continued to build support for a caretaker mayor, proposing candidates they preferred to Breed. With city leaders maneuvering against one of its most prominent black residents, it seemed to Breed’s friends like history was about to repeat itself.

“They have pushed out African Americans,” said Sheryl Davis. “And everybody talks about how diverse and progressive we are. But if it happened anywhere else, we’d be saying what a tragedy.”

Davis added that “people are happy to see her run, but I also think that people are so cynical that they don’t really think San Francisco is going to give her a fair shot.” She made it clear she was only speaking personally, as Breed’s friend and colleague and, perhaps most of all, as Henry Davis’ mother.

“Ask yourself, how did we get to where we are in this city?” said Jim Stearns, a consultant for former state Sen. Mark Leno, one of Breed’s opponents for mayor. “Well, the people who are leading this city right now like London Breed have to take responsibility for that. They have to be held accountable. And if you want change, you need new leaders to start with.”

Breed’s critics tend to argue that her biography, while powerful, is all she has to offer. They say she’s an actress, someone who knows how to sell her story but lacks major legislative achievements. To them she is little more than an apparatchik of the establishment, the next in a line of candidates backed by former Mayor Willie Brown and rich donors like tech mogul Ron Conway.

The battle over Breed’s incumbency came to a head on Tuesday, when supervisors scheduled a vote to appoint a caretaker mayor. The public was invited to weigh in. For hours, residents filed up at the podium and spoke in two-minute bursts.

Proponents of a caretaker often quoted from the dry language of the City Charter; they emphasized rules, procedures, the need for “fairness” to all candidates. Breed’s supporters, both black and white, quoted from the Charter, too, but they also invoked San Francisco’s racial legacy. Blacks in San Francisco have never had a level playing field, they said. Removing Breed, many argued, would be an act of racism.

One black woman, Linda Yoakum, an advocate for residents of a housing co-op in the Western Addition, told a story about how Breed had helped her after the tragic drowning of a daughter, who left behind three children. Yoakum said that Breed appeared on her doorstep to offer support, then made sure that the three now-motherless grandchildren didn’t lose housing.

The two-minute bell sounded, but Yoakum said she was going to finish what she had to say. She raised a book high over her head. Every one of those grandchildren had made it through school, she said. One had just completed nursing school at UCLA. This was her commencement book.

Mattie Scott, who’d been at the gun-buyback event and the rally at the Fillmore arcade, spoke softly. Her family had moved here from Louisiana, where she’d been raised. “It feels like Jim Crow has crept back up, in San Francisco,” she said.

And then, suddenly, it was over. In the culmination of weeks of secret negotiations, six members agreed on a caretaker mayor: Supervisor Mark Farrell, a moderate like Breed, but almost her perfect inverse in every other respect — a white venture capitalist, educated at an elite city prep school.

Farrell was quickly sworn in, his family at his side. City Hall soon sent out the usual email containing the mayor’s next-day schedule:

Wednesday, January 24

Mayor Mark Farrell to conduct meetings at City Hall.

Breed’s tenure had lasted just more than 42 days.

“It hurts like hell,” Scott would say after the vote. “Goddamn — we’re in 2017 and we still gotta deal with this. ... It was like, you’re all talking about Donald Trump, but your characters just all displayed what’s going on in Washington, D.C. How can you open your mouth about Donald Trump?”

Breed herself has expressed gratitude for such sentiments, but otherwise has remained silent about the vote and the dealings that led to it. “I will continue to do all that I can to take care of this city,” she said in a brief statement.

But days before, sitting for an interview at City Hall, she had struck a more defiant note.

“I don’t do this job in fear of losing it,” she said. “For me — I’ve been poor. I’m not scared to go back there.”

She also pondered the question: What would it mean if she were ousted as acting mayor?

“You mean by my colleagues?” she said. She clucked her tongue, leaned forward.

“I’m still president of the board,” Breed said. “I’m still District Five supervisor.”

No hesitation. No smile.

“And I’m still running for mayor.”

Jason Fagone is a San Francisco Chronicle staff writer. Email: jason.fagone@sfchronicle.com Twitter: @jfagone