California Code, Elections Code - ELEC § 7400

In each county containing less than five Assembly districts, a county central committee shall be elected by supervisor districts, and the number to be elected from any supervisor district shall be determined as follows: There shall be taken the number of votes cast in the supervisor district at the last gubernatorial election for that party's candidate for Governor, or, if the party had no candidate for Governor, for the candidate of the party voted on throughout the state who received the greatest number of votes and who was the candidate of that party alone. This number shall be divided by one-twentieth of the number of votes cast in that county for Governor or, where the party had no candidate for Governor, for the candidate mentioned above. The integer next larger than the quotient obtained by such division shall constitute the number of members of the committee to be elected by that party in that supervisor district.

The committees in counties containing less than five Assembly districts shall be composed of not less than 21 members. If the procedure outlined above would result in less than 21 members being elected for any committee, the number of votes cast for this party's candidate in each supervisor district shall be divided by an amount sufficiently smaller than one-twentieth of the votes cast for Governor in that county as to give a membership in the committee equal to or the nearest amount which is greater than 21 members.