Mayor Daniel Lurie has indicated support for the measure. If approved by voters, the tax would direct funds not only to the San Francisco Municipal Transportation Agency but also to BART, AC Transit, Caltrain, the Santa Clara Valley Transportation Authority, the Contra Costa County Transportation Authority, the San Mateo County Transit District, and additional regional operators.

The signature margin — 65 percent above the minimum required — gives backers a visible head start heading into the campaign season, though qualifying and winning are different hurdles. Parcel taxes in California typically require two-thirds approval from voters, a bar that has tripped up transit measures before.

The measure's regional scope adds complexity. Revenue would flow to multiple agencies across several counties, and the measure does not require passage in every county to take effect. That structure has already drawn scrutiny from riders in areas skeptical about how their tax dollars would be managed by agencies with mixed delivery records.

SFMTA faces a well-documented structural deficit, and the agency has warned of service cuts if new revenue isn't secured before existing federal pandemic relief funds expire. The parcel tax is one of several funding proposals in circulation, but it is now the one with a confirmed place on the ballot.

Watch for: the official November ballot title and impartial analysis from the City Attorney's office, the formation of formal campaign committees, and any Board of Supervisors action on competing transit funding proposals before the election.