CA Pub Util Code Section 102333

The district may conduct a single election in an area comprising the area of a city and the unincorporated area of a county or more than one unincorporated area of a county or counties, or any combination of those areas, with the approval of the cities and counties concerned, in which event two-thirds of the voters voting at the election shall be sufficient to approve the proposition submitted for the entire area included in the election. Where more than one election will be held, the approval of the voters in one election pertaining to an area may be conditioned upon the approval of voters in one or more other elections pertaining to other areas.