Except as limited by this charter, the legislative powers of the city shall be vested in a city council consisting of seven members. Four members shall be residents of and elected from the four wards in the city, one member from each ward, and three members shall be elected at large. Except as necessary in the case of vacancies, members representing each ward shall be elected in the regular municipal election held in the year immediately prior to the year in which a presidential general election is held; and members at large shall be elected in the regular municipal election held in the year immediately following the year in which a presidential general election is held. All members of council shall serve for a term of four years commencing on January 1 of the year following the date of the member's election.