If either the office of tax assessor or the office of tax collector becomes vacant before the expiration of the term of office and before the time of the election provided by this subpart, the remaining officer shall serve in an acting capacity for the vacant office without additional compensation until the remaining provisions of this subpart become operative or have no further effect. If this subpart becomes operative, the remaining officer shall be the county revenue commissioner for the remainder of the term for which he or she was elected.