As used in this Division: Emergency interim successor shall mean a person designated pursuant to this Division for possible temporary succession to the powers and duties, but not the office, of a County officer in the event that such officer or any duly authorized deputy is unavailable to exercise the powers and discharge the duties of the office. Unavailable shall mean either that a vacancy in office exists and there is no deputy authorized to exercise all of the powers and discharge the duties of the office, or that the lawful incumbent of the office (including any deputy exercising the powers and discharging the duties of an office because of a vacancy) and his duly authorized deputy are absent or unable, for physical, mental or legal reasons, to exercise the powers and discharge the duties of the office.