Cal. ELEC § 7404

(a) In each county, the nominee of the party for State Senator, the nominees of the party for the Assembly, and any person nominated to either the Senate or Assembly at a special election to fill a vacancy in the house, and the nominee of the party for Representative in Congress shall be ex officio members of this committee. If the person most recently nominated or elected from one party at the special election for an Assembly or Senate seat, or for the House of Representatives shall be other than the nominee of that party for the same office at the earlier election, the ex officio membership of the latter nominee shall expire immediately upon certification by the Secretary of State of the nomination or, if there is no runoff, the election of the person most recently nominated or elected. Ex officio members shall be entitled to all the rights and privileges, including the right to vote, and shall have the same standing in every way as other members of this committee, except they shall not be entitled to a ballot designation of incumbent upon seeking election to this committee in the next presidential primary. A person shall be entitled to ex officio membership upon receiving a certificate of nomination from the Secretary of State pursuant to Section 8147, at which time the term of the former nominee shall expire.

(b) If the person most recently nominated to the Senate, Assembly, or House of Representatives received fewer votes for the particular office at the ensuing general election than a write-in candidate for the same office, and the write-in candidate is elected to that office, the write-in candidate shall, for purposes of this part, be considered the ex officio member of each affected county, provided that the write-in candidate’s affidavit of registration reflects that that candidate has been affiliated with the party for at least six months prior to the general election.

(c) If a write-in candidate is entitled to ex officio membership on each affected county central committee pursuant to subdivision (b), each affected county central committee shall designate the party nominee described in subdivision (b) as an additional ex officio member to its committee. Any person designated as an ex officio member under this subdivision shall be entitled to all the rights and privileges as other ex officio members of the committee.