In a surprise reversal of its previous decisions, the Board of Supervisors voted unanimously on Tuesday to delay a major, 157-unit Mission District housing project on South Van Ness Avenue near 26th Street.

Supervisor David Campos said he changed his mind at the last-minute and moved to support the appeal and delay the project after hearing “hateful and divisive” comments during the public hearing.

“I came into this hearing thinking that I would vote against the appeal,” he said. “But for those of you who always wondered does public comment make a difference, I think this area is a perfect illustration that it does.”

The decision concerned a housing development at 1515 South Van Ness Ave., which activists were appealing on environmental grounds — an argument that they have lost in delaying other projects.

They argued Tuesday – as they have unsuccessfully in the past – that the project’s impact on gentrification should be studied before it went forward.

Campos said those arguments won on Tuesday in part because of what he described as hateful comments made by Sonja Trauss, founder of the San Francisco Bay Area Renters Federation.

Trauss, speaking in support of the project, compared activist opposition to new market-rate housing in the Mission to the racist rhetoric of Donald Trump. By preventing new housing, activists were being as unwelcoming of newcomers as Trump, Trauss said.

“When you come here to the Board of Supervisors and say that you don’t want new, different people in your neighborhood, you’re exactly the same as Americans all over the country that don’t want immigrants,” she said. “It’s the same attitude, it’s the exact same attitude.”

Supervisor Aaron Peskin shook his head as Trauss spoke and sprang out of his seat, walking over to Supervisor David Campos across the chamber room. After another speaker lambasted activists for doing nothing about Mission gangs in the 1990s and called them hypocritical for only caring about the neighborhood now, it became clear that Campos was furious.

He conferred with Supervisor Peskin and walked over to Supervisor John Avalos before returning to his seat. He then moved to delay the project until further study could be done by the city.

“If there’s ever a time to stand by doing what is right, that is today,” he said.

The board voted 9-0 to uphold the appeal — Scott Wiener and Norman Yee were absent. The vote means the 157-unit project put forward by Lennar Multifamily Communities will be delayed until the city conducts further study.

At issue in the appeal was what activists called an outdated Eastern Neighborhoods Plan, which governs development in the Mission District, Potrero Hill, Dogpatch, and Central SoMa. The plan, adopted in 2008, exempts projects that meet its guidelines from specific environmental review, a major sticking point for activists who say they are being waved through without regards to their full impact.

The board’s decision comes after supervisors in the last five months have twice voted overwhelmingly against appeals launched on similar grounds.

In July, a 395-unit development at 901 16th St. in Potrero Hill was cleared by the board 9-1.

In September, the same appellants who testified on Tuesday gave similar arguments about gentrification and displacement in appealing a 330-unit project at 2000 Bryant St. in the Mission — but the project was unanimously approved after city staff said concerns about affordability should not be addressed under the state’s environmental law, known as the California Environmental Quality Act.

Though city staff made the same argument on Tuesday, supervisors went against their analysis and recommended that the city study the “cumulative impacts” of market-rate projects coming to the eastern half of the city.

“We are not paying attention to the entire environment, to the entire landscape,” said Supervisor Malia Cohen. “We are becoming out of balance, and it’s important for us to be in sync.”

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Supervisor Campos, for his part, said the appellants “have to do a better job” connecting the issue of displacement with the specific legal issue based on the state’s environmental law.

“I’m not happy [with] what was presented by the appellants,” he said. “I don’t think they did a good enough job in many respects.”

Nevertheless, he later voted in favor of the appeal.

The Lennar development had reached an affordability milestone in August by making 25 percent of its units available to low and middle income tenants. It was the first project in San Francisco to accomplish the feat without public subsidy or upzoning.

The discussion on Tuesday steered away from affordability questions per se, though activists said they wanted a third or more of the units to be below-market-rate.

It’s unclear whether Tuesday’s decision holds legal muster, since the appeal was based strictly on the state environmental law. Campos himself said he could be open to lawsuits, but was largely unperturbed.

“Bring it on,” he said.

Trauss said no single public comment from the audience should change the board’s mind “since it’s a legal question” whether the project should be approved.

Trauss’s comment was not the only Trump-related one made during the three-hour public hearing.

Spike Kahn, a landlord who owns several buildings throughout the city and is the founder of the Pacific Felt Factory arts space, said that in the wake of Trump’s election city supervisors had a particular obligation to “take a stand to protect our neighbors” by blocking projects in minority neighborhoods like the Mission.

“How can we do better to walk the walk than to protect the Mission and our Latino community members?”

Rick Hall, a neighborhood activist, drew a parallel between San Francisco’s sanctuary city status and the recent increased development. He said instead of being a sanctuary city for immigrants and others, the city welcomed only wealthy newcomers.

“We will be a sanctuary city, but only to the undocumented rich,” he said.

It was the comments made by those supporting the project, however, that upset supervisors. Many said those experiencing gentrification should be addressed more respectfully.

Outside the chamber halls, it was a rare moment of happiness for Mission District activists. Typically a quiet crowd after housing decisions at City Hall, they were elated with what they called a “shocking” victory.

“We think it’s the right decision,” said Peter Papadopoulos, a lead activist against market-rate development. “The impacts are clear.”

Scott Weaver, a tenants rights attorney who took the lead in opposing the project and argued the appeal, said Campos sided with them because the project is in the Latino Cultural District and that he has an “affinity” for the designation.

The Latino Cultural District is a symbolic designation by the city of the area around 24th Street. It has no housing guidelines, though Campos previously urged that all market-rate development be stopped in the area. Several speakers argued that the culture of the neighborhood would be eroded if more market-rate projects were allowed in.

It’s unclear what’s next for the Lennar development. It must wait for the city to conduct further study, though it’s unclear whether the project would go forward as envisioned or not.

Regardless, the Board of Supervisors is set to see more such appeals. A 117-unit development at 2675 Folsom St. in the Mission will be appealed on the same environmental grounds as the South Van Ness development by the same activists. If today’s decision is any indication, it too may be delayed.