Cal. Elec. Code § 7208
A committee may authorize any member of that committee, whether elected or ex officio, to appoint an alternate if a member desires to appoint an alternate. An incumbent Member of the Senate or Assembly at the time of the meeting of the committee may appoint an alternate member without authorization from that committee, if the member desires to appoint an alternate.
That alternate member shall have the right to vote only with the written authorization of the member who appointed him or her. An alternate member of a county central committee shall be subject to the rules and regulations of the committee.
An alternate member must meet the same qualifications as the regular member and may vote only in the absence of the member who appointed him or her.
Ca. Elec. Code § 7208