Mich. Comp. Laws § 168.192

Sec. 192. A general primary election of all political parties shall be held in every county of this state on the Tuesday succeeding the first Monday in August preceding the general November election at which the officers named in section 191 of this act are to be elected, at which time the qualified and registered electors of each political party may vote for party candidates for the offices. This section shall not apply to parties required to nominate candidates at caucuses or conventions.