Wiener, a Democrat who holds the 11th Senate District seat, threw his support behind Haney as the race to replace him takes shape. Haney, also a Democrat, represents the 17th Assembly District and won reelection handily on Tuesday.

In a statement, Wiener pointed to a decade-long working relationship with Haney, citing his record on building housing, holding powerful corporations accountable and lowering costs for working families.

"Matt is the champion San Francisco needs," Wiener said.

Christine Pelosi, the daughter of retiring Rep. Nancy Pelosi, is also running for the seat. A longtime Democratic Party figure, Christine Pelosi has never held elected office.

The endorsement comes as Wiener prepares to leave the Legislature for Washington. A special election will be held early next year to fill the Senate seat.

Wiener's backing gives Haney a prominent ally in a contest that is likely to draw attention well beyond San Francisco, given the Pelosi name and the national profile of California's housing and affordability debates. Haney has built his Assembly record around housing production and tenant protections, positions that align with the progressive wing of the party that Wiener has often represented.

The race will test whether voters favor Haney's legislative experience and Wiener's endorsement or the name recognition and party connections that Christine Pelosi brings to her first run for office.