AZ Rev Stat § 11-211 (2021)
2021 Arizona Revised Statutes|Title 11 - Counties|§ 11-211 - Membership; qualifications; term

11-211.  Membership;  qualifications;  term A. There shall be in each county having a population of one hundred seventy-five thousand or more persons a board of supervisors consisting of five members who shall be qualified electors of their supervisorial district,  and who shall be elected at a general election at which the president of the United States is elected. In each county having a population of less than one hundred seventy-five thousand persons,  a board of supervisors shall consist of three members,  except as prescribed by subsection B or C of this section,  who shall be qualified electors of their supervisorial district and who shall be elected at a general election at which the president of the United States is elected. They shall enter on their duties on January 1 subsequent to their election,  and shall hold office for four years. No person holding any other county or precinct office is eligible to the office of supervisor. B. Any county having a population of less than one hundred fifty thousand persons but more than one hundred thousand persons shall call an election to change from a three-member to a five-member board of supervisors,  or from a five-member to a three-member board of supervisors,  on receipt by the board of supervisors of a petition containing signatures of qualified electors equal to at least ten percent of the votes cast in the county at the preceding general election at which a president of the United States was elected. The board shall submit to the electors in the county,  at a special election called for that purpose,  the question whether or not the county shall elect five members or three members to the board of supervisors. The election shall be held before the first Monday in January preceding the next general election. The ballots shall contain the words: " Five supervisors,  yes. Five supervisors,  no."  or " Three supervisors,  yes. Three supervisors,  no."  If the majority of the qualified electors voting on the question votes in the affirmative,  the board of supervisors shall redistrict the county in accordance with section 11-212. The county shall thereafter elect the prescribed number of members to the board of supervisors who shall be elected in the manner provided in subsection A of this section and have the same qualifications as provided in subsection A of this section for a board of supervisors with a population of one hundred seventy-five thousand or more persons,  and shall hold office for a term of four years to commence on January 1.  C. Any county having a population of at least one hundred fifty thousand persons but not more than one hundred seventy-five thousand persons and having a county board of supervisors that consists of three persons shall submit to the electors in the county,  at the next general election after the release of the population estimate from the office of economic opportunity,  the question of whether the county shall elect five members to the board of supervisors. The ballots must contain the words: " Five supervisors,  yes. Five supervisors,  no."  If approved by a majority of the qualified electors of that county who voted on the question,  the board of supervisors shall redistrict the county pursuant to section 11-212. The county thereafter shall elect at the next general election immediately following the election at which the question is approved the prescribed number of members to the board of supervisors who shall have the same qualifications as provided in subsection A of this section. The following apply to the election for the county board of supervisors prescribed in this subsection: 1. If the next general election immediately following the election at which the question is approved is held in a year that is the last year of the four-year term of the three members of the county board of supervisors who are already holding office,  the five persons elected to the county board of supervisors hold office for a term of four years to commence on January 1 immediately following their election. 2. If the next general election immediately following the election at which the question is approved is held in a year that is not the last year of the four-year term of the three members of the county board of supervisors who are already holding office,  the two additional persons elected to the county board of supervisors hold office for a term of four years to commence on January 1 immediately following their election. The three members of the county board of supervisors who are already holding office continue to serve their four-year terms of office without regard to whether they are residents of the newly redrawn supervisorial districts for the remainder of those four-year terms. Thereafter,  members of the board of supervisors must be residents of their supervisorial district and the term of office for members of that county board of supervisors shall be staggered four-year terms. 3. For the election at which the question of whether the county shall elect five members to the board of supervisors is on the ballot,  the county shall include in the publicity pamphlet an estimate of the cost to the county for each additional member to the board of supervisors. 4. For the purposes of this subsection,  " population"  means the population according to the annual population estimate provided by the office of economic opportunity.