Idaho Code § 50-612

A city may, by ordinance, provide that a majority of the votes for any candidate running for the office of mayor shall be required for election to that office. In the event no candidate receives a majority of the votes cast, there shall be a runoff election between the two (2) candidates receiving the highest number of votes cast. Such runoff election shall be conducted by the county clerk as in the general election in a manner consistent with chapter 14, title 34, Idaho Code, and at such time, within thirty (30) days of the general election, as prescribed by the city and shall be exempt from the limitation upon elections provided in sections 34-106 and 50-405, Idaho Code. The ballot shall be prepared by the county clerk not less than twenty-two (22) days preceding the runoff election. The designation of polling places shall be made by the county commissioners not less than twenty (20) days preceding any runoff election and sample ballots shall be printed not less than eighteen (18) days preceding the runoff election.