On December 27, five Michigan voters filed a lawsuit against the Governor, to force him to call a special election sooner than November 2018 to fill the vacancy in the 13th U.S. House district. See this Courthouse News Story. The district currently has no representative because Congressman John Conyers resigned last month.
The case is Rhodes v Snyder, e.d., 2:17cv-14186. It is assigned to Judge Mark A. Goldsmith, an Obama appointee. Thanks to Thomas Jones for this news.