Tenn. Code § 8-48-111
This section shall be applicable to officers of political subdivisions, including, but not limited to, cities, towns, villages, townships and counties, as well as school, fire, power and drainage districts, not included in § 8-48-110. Such officers, subject to such regulations as the executive head of the political subdivision may issue, shall designate by title (if feasible) or by named person, emergency interim successors and specify their order of succession. The officer shall review and revise, as necessary, designations made pursuant to this section to ensure their current status. The officer will designate a sufficient number of persons so that there will be not less than three (3), nor more than seven (7), deputies or emergency interim successors or any combination thereof, at any time. In the event that any officer of any political subdivision, or the officer's deputy provided for pursuant to law, is unavailable, the powers of the office shall be exercised and duties shall be discharged by the officer's designated emergency interim successors in the order specified. The emergency interim successors shall exercise the powers and discharge the duties of the office to which designated until such time as a vacancy which may exist shall be filled in accordance with the constitution or statutes, or until the officer, or the officer's deputy or a preceding emergency interim successor, again becomes available to exercise the powers and discharge the duties of office.
T.C.A. § 8-48-111