The measure authorizes the creation of a municipal finance corporation, a city-owned entity that could eventually become a full-fledged public bank. Such an institution would be able to issue loans for public-interest projects including housing, environmental protection, and community infrastructure.

"Together we made history, and in 100 years San Franciscans will assume the Public Bank has always been here to provide for us, like our airport, our roads, like the very water from the Hetch Hetchy," said Misha Steier, spokesperson for the San Francisco Public Bank Coalition, in a statement. The coalition, founded in 2017, has spearheaded the public bank effort.

The measure's victory was not assured on election night, when it trailed narrowly at 49.8% to 50.2% with a margin of just 630 votes. It gained ground as later ballot returns came in and reversed course two days later on Nov. 5, with subsequent returns leaning progressive.

Supervisor Jackie Fielder, a progressive who co-founded the coalition and has been one of the measure's most vocal champions, framed the win in terms of economic and climate justice. "As working San Franciscans struggle with the rising cost of living and the growing threat of climate crisis, we need public institutions that aspire to reimagine how we can invest in our communities and in solutions that address climate change," Fielder wrote in a statement.

The new municipal finance corporation will start with the help of banking professionals, a board of directors, and oversight commissions. Funding sources would include federal funding, state grants, and philanthropic giving. To become a full public bank, the corporation must demonstrate a record of success over its first three years, then apply for a state banking charter and obtain approval and licensing from the California Department of Financial Protection and Innovation, along with Federal Deposit Insurance Corporation deposit insurance.

Supervisor Chyanne Chen, another progressive supporter on the Board of Supervisors, pointed to the broader political context. "I'm especially excited because with Democrats in control of the House and Senate, there may be new avenues available to fund the bank, so that we can get work financing the things we need," Chen wrote in a statement, referencing the midterm elections that gave Democrats majority control of both chambers of Congress.

Opposition to the measure was modest. Critics argued that creating a public bank would be costly and that running such a complicated financial institution posed too many risks. Mayor Daniel Lurie opposed Proposition B but did not actively campaign against it. The group GrowSF and the think tank SPUR were behind a modicum of opposition spending.

The approval marks a significant milestone for the city's progressive movement, which has long floated the idea of a public bank that would reinvest public money back into the community. "This victory shows that nothing is beyond grassroots power," Steier said. "On we march."