Compiled Laws, Chapter 168. Michigan Election Law § 168.594

Sec. 594. The county conventions of all political parties for the election of delegates to a state convention in the odd numbered years shall be held not less than 7 days before said state convention. All such county conventions of any one political party shall be held on the same day throughout the state, which day shall be designated by the state central committee of such political party in its call for the state convention provided for in section 593 of this act.  1 The place and hour of meeting of any such county convention shall be designated in the call issued therefor by the county committee of such political party in the county, which call shall be issued not less than 15 days before such county convention. The number of delegates to the state convention to which such political party in such county is entitled shall be chosen at such county convention. In all counties having or which may hereafter have 2 or more congressional districts or parts of congressional districts within the boundaries of the county, such congressional districts or a part of any congressional district within said counties shall each be considered a county within the provisions of this section for the holding of county conventions provided for in this section, and shall be in lieu of said county conventions. The nominee for congress of the congressional district in the preceding primary election, the county chairman and the county secretary of the several political parties shall constitute a committee in each congressional district to name the temporary chairman of the first district convention held under this act. Thereafter, the district chairman shall act as temporary chairman. The said convention shall then proceed to organize the same as county conventions and shall proceed to the election of delegates to the state convention. The chairman and secretary of any such convention shall certify to the state central committee the names and addresses of the delegates so elected, and when so certified they shall become the delegates from said district to the state convention.