California Code, Elections Code - ELEC § 10418

(a) Whenever an election is to be held on the same day as a statewide election, a special election, or an election held pursuant to Section 1302 or 1303, the election may be consolidated with the statewide or special election, or the election held pursuant to Section 1302 or 1303, as applicable. If consolidated, the consolidated election shall be held and conducted, election boards appointed, voting precincts designated, candidates nominated, ballots printed, polls opened and closed, voter challenges determined, ballots counted and returned, returns canvassed, results declared, certificates of election issued, recounts conducted, election contests presented, and all other proceedings incidental to and connected with the election shall be regulated and done in accordance with the provisions of law regulating the statewide or special election, or the election held pursuant to Section 1302 or 1303, as applicable.

(b) The precincts used at the consolidated election shall be those used for the statewide, special, or regularly scheduled election and, where necessary, the county elections official may adjust precinct lines to coincide with the boundaries of the particular jurisdiction.