Cal. Elec. Code § 7406
A committee may authorize each elected member and each ex officio member of that committee to appoint an alternate member. An ex officio member who is also an incumbent officeholder of any of the offices listed in Sections 7404 and 7405 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.
The 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 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, except that an alternate member appointed by an incumbent Senator, Member of the Assembly, or Representative in Congress need not reside in the district of the appointing power but need only reside in the county of jurisdiction of the committee.
Ca. Elec. Code § 7406