SECTION 604. VACANCY.
   The City Council, by a vote of at least three of its members, may appoint a replacement to fill any vacancy on the City Council. Such appointee shall hold office until a successor is elected and certified. If the vacancy occurs before the first day to file nomination papers for the next general municipal election, a Council Member shall be elected at that election as the successor to any appointee, or to fill the vacancy if it has not previously been filled by appointment, and such newly elected Council Member shall serve the remainder of the unexpired terms and until a successor is elected and certified.
   If a vacancy is not filled by appointment within 30 days after its occurrence, the City Council shall immediately call a special election to fill the vacancy. The special election shall be held not later than 120 days after the vacancy occurs, except that no special election shall be called to fill the vacancy if it cannot be held at least 180 days before the next general municipal election. A person elected at a special election shall hold office for the remainder of any unexpired term and until a successor is elected and certified.
   If there is an election to fill one or more full terms and one or more unexpired terms, then the candidates who receive the highest number of votes shall serve the full terms, and of the candidates remaining, those who receive the next highest number of votes shall serve the unexpired terms.
   At any time when there are three or four vacancies on the City Council, the remaining Council Member or Members shall constitute a quorum for the purpose of holding a meeting to consider taking action pursuant to this section, and such action may be taken by the unanimous vote of the remaining Member or Members.