Cal. Elec. Code § 13300

(a) By at least 29 days before the partisan primary, each county elections official shall prepare a separate sample ballot for each political party and a separate sample nonpartisan ballot. The county elections official shall place on each ballot, as applicable, in the order provided in Chapter 2 (commencing with Section 13100), and under the appropriate title of each office, the names of all candidates for whom nomination papers have been duly filed with him or her, or have been certified to him or her by the Secretary of State, to be voted for in his or her county at the partisan primary election.

(b) The sample ballots shall be identical to the official ballots, except as otherwise provided by law. The sample ballots shall be printed on paper of a different texture from the paper to be used for the official ballot.

(c) One sample ballot of the party for which the voter has disclosed a preference, as evidenced by his or her registration, shall be mailed not more than 40 nor fewer than 10 days before the election to each voter entitled to vote at the primary who registered at least 29 days prior to the election. A nonpartisan sample ballot shall be so mailed to each voter who is not registered as preferring any of the parties participating in the primary election, provided that on election day the voter may, upon request, vote the ballot of a political party if authorized by the party’s rules, duly noticed to the Secretary of State.