In each county where the number of members of central committees to be elected is 12 or less, the members shall be elected in a countywide, at large district. In each county where the number to be elected is 13 or greater, the members shall be elected by supervisorial district, except in Los Angeles County and in the City and County of San Francisco, wherein the members shall be elected by Assembly district.
Ca. Elec. Code § 7753