Whenever a vacancy for any cause whatever shall occur in any elective office, the Council, by a majority vote of its duly elected or appointed members present at a regular meeting held not less than fifteen or more than thirty days following the occurrence of such vacancy, shall elect a qualified person for such office who shall hold office until the next City election and until his successor shall have been elected and qualified; provided, however, that any vacancy in the office of Council member shall be filled by a person of the same political affiliation as the Council member whose office is vacant. In the event the Council shall fail to elect a qualified person to the office of Council member within thirty days after the occurrence of such vacancy, the Mayor shall appoint a qualified person therefor.