San Mateo County, California has until August 11 to join San Francisco, Alameda, and Contra Costa counties on a 2026 regional ballot measure to fund transit. According to this, the deadline is August 11. This market resolves yes if San Mateo County opts in.

https://www.greencaltrain.com/2025/06/opt-in-counties-san-mateo-and-santa-clara-set-timelines-for-regional-measure-decision/