California Code, Elections Code - ELEC § 12306

The county elections official of any county, in appointing members of the several precinct boards to serve in the direct primary and general elections under the provisions of this code, shall permit the county central committee of each qualified political party to nominate for appointment to the precinct board a member of that party who is registered and resident in that precinct.  Nomination pursuant to this section shall be made in writing to the county elections official not less than 90 days before the election for which the nomination is made.  In making appointments to precinct boards from nominations submitted by political parties, the county elections official shall give preference to the nominee of any qualified political party with at least 10 percent of the registered voters in the precinct for which the nomination is made.