Montana constitution
Article VI: the executive
Section 6

(2) If the office of secretary of state, attorney general, auditor, or superintendent of public instruction becomes vacant by death, resignation, or disability as determined by law, the governor shall appoint a qualified person to serve in that office until the next general election and until a successor is elected and qualified. The person elected to fill a vacancy shall hold the office until the expiration of the term for which his predecessor was elected.