The move comes as polling suggests Chan has closed ground on Chakrabarti, who entered the race with substantial self-funding and early name recognition built outside San Francisco. Chakrabarti has reported spending roughly $10 million of his own money on the race. Chan, by contrast, has leaned on organized labor — SEIU, building trades, and other union affiliates — whose door-knocking and phone-bank operations can substitute for cash in a primary where turnout patterns are unpredictable.

Chan's union backing is not symbolic. Labor-backed ground games have moved close primaries in San Francisco before, and the supervisor has held her Board seat in the northeast corner of the city through two cycles. Her challenge is name recognition outside District 1. The congressional district runs from the Richmond and Sunset through Daly City, and Chan's campaign has not matched her rivals' paid media presence citywide.

The third major candidate in the race, Stephen Whitburn, remains a factor. The top-two primary format means the fight is not simply about winning — it is about finishing in the top two, and a crowded field compresses those margins.

Chakrabarti's campaign has drawn criticism in online forums for focusing on national progressive credibility rather than district-specific policy. Some voters have flagged his limited prior ties to San Francisco as a liability. His campaign has received endorsements from Rep. Ilhan Omar, among others.

The primary is June 3. Watch for updated independent expenditure filings from labor committees and whether Chan's ground operation translates to early-vote returns, which the registrar will begin releasing election night.