Compiled Laws, Chapter 168. Michigan Election Law § 168.105

Sec. 105. Whenever a vacancy shall occur in the office of United States senator, the governor shall appoint, to fill the vacancy, some suitable person having the necessary qualifications for senator. The person so appointed shall hold office from the time of his appointment and qualification until the first day of December following the next general November election which occurs more than 120 days after such vacancy happens. At such general November election, a United States senator to fill such vacancy shall be elected and the person so elected shall hold office from the first day of December following such election for the balance of the unexpired term of the senator whose vacancy is filled.