Whenever a vacancy in the office of mayor shall occur by reason of death, resignation, removal, or any other cause, including physical or mental incapacity, the senior member of the commission based on consecutive time in service as commissioner shall serve as acting mayor until an acting mayor is selected by the commission. An acting mayor shall be selected by a majority vote of the commission and shall assume the duties of the office of mayor effective on the date selected and shall serve as acting mayor until a new mayor is elected and qualified as hereinafter provided. The acting mayor shall receive no compensation, expenses, or allowances as a commissioner while acting as mayor, but shall receive the same rate of pay and allowances provided for the mayor whose vacated office the acting mayor fills. The election commission of the city, if there be one, and if not then the commission thereof, shall within five days of the occurrence of a vacancy in the office of mayor call a special election to fill the vacancy, the election to be held on a Tuesday not less than 30 days and not more than 60 days from the occurrence of the vacancy. Notwithstanding the foregoing, if a regular or special election is scheduled or required to be held within 90 days after the occurrence of the vacancy but more than 30 days after the occurrence, then the vacancy in the office of mayor will be filled at the regular or special election. Notice of the election shall be given at the expense of the city by one publication at least 18 days in advance of the election in one or more newspapers published in the city. The method, procedure, and requirements of qualifying, voting upon, and determining the successful candidate shall be the same as is provided herein relative to the election of the mayor at regular elections, except that statements of candidacy must be filed at least 20 days before the date set for such election. The successor to the mayor chosen at any such election shall qualify for office as soon as practical thereafter, and shall be clothed with and assume the duties, responsibilities, and powers of such office immediately upon qualification and shall hold office for the unexpired term of the predecessor and until a successor is elected and qualified.