(1) Upon the adoption of the form of government provided in this chapter, 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.