(1) The legislative authority of the county shall be vested in a board of county commissioners comprised of three (3), five (5) or seven (7) members. The petition or resolution shall specify the size of the board of county commissioners and shall indicate the term of office of the commission, as provided in section 31-5305, Idaho Code. In no event shall the term of office of any incumbent member of the board of county commissioners be affected as a result of an increase in the size of the board of county commissioners under the provisions of this chapter.
(2)  If the size of the board of county commissioners is increased, at the regular meeting of the board in January, preceding any election of additional county commissioners, the board must divide the county into the number of districts equal to the number of commissioners approved by the electors. The districts established shall be as nearly equal in population as possible. The redrawing of an existing district which places the incumbent county commissioner for that district outside of its boundaries shall not disqualify or otherwise affect the qualifications of the commissioner during his incumbency.