Tenn. Code Ann. § 8-48-101: Causes of vacancies

Any office in this state is vacated by:

(1) The death of the incumbent;

(2) The incumbent's resignation, when permitted by law;

(3) Ceasing to be a resident of the state, or of the district, circuit, or county for which the incumbent was elected or appointed;

(4) The decision of a competent tribunal, declaring the election or appointment void or the office vacant;

(5) An act of the general assembly abridging the term of office, where it is not fixed by the constitution;

(6) The sentence of the incumbent, by any competent tribunal in this or any other state, to the penitentiary, subject to restoration if the judgment is reversed, but not if the incumbent is pardoned; or

(7) Due adjudication of the incumbent's insanity.