Cal. Elec. Code § 7228

If the elections official, on the 73rd day prior to the direct primary election, finds that the number of candidates nominated for election to a committee from an Assembly or supervisorial district does not exceed the number of candidates to be elected from that Assembly or supervisorial district, the designation of the office and the names of the candidates shall not be printed on this party’s ballot in the Assembly or supervisorial district, unless there is filed with the elections official, not later than 20 days after the final date for filing nomination papers for the positions, a petition indicating that a write-in campaign will be conducted for the office and signed by 25 registered voters affiliated with the political party involved. In lieu thereof, the board of supervisors shall declare elected the candidates who have been nominated, and those candidates shall be entitled to receive certificates of election in the same manner as other candidates elected to a committee.