AZ SB1428

Establishes a tiered county board of supervisors membership based on population: 3 members for counties under 175,000; 5 members for 175,000 to under 1 million; 7 members for 1 million to under 3 million; and 9 members for counties with 3 million or more residents

Allows counties with populations between 100,000 and 150,000 to petition for an election to change between 3 and 5 board members, requiring signatures equal to 10% of votes cast in the preceding presidential election

Requires counties to redistrict into 3, 5, 7, or 9 supervisorial districts following the release of U.S. decennial census data, with districts having no more than 10% population difference

Applies the same tiered membership structure to county supervisors serving on regional public transportation authority boards

Takes effect December 31, 2032