The suit was filed in Detroit federal court by the Michigan League of Women Voters and 11 Democrats, including two former lawmakers. It came as the U.S. Supreme Court considers, in a case from Wisconsin, whether there can be too much politics in the once-a-decade task of drawing electoral districts.
"The Michigan Legislature intentionally drew legislative lines invidiously, to marginalize Democratic voters and dilute their votes solely because they were not Republicans. This violates legitimate redistricting principles and reflects no legitimate legislative objective," wrote the lawyers, who include former Michigan Democratic Party Chairman Mark Brewer.
The complaint alleges that Republicans, who have controlled the Legislature since 2011, gerrymandered by "cracking" and "packing" Democratic voters while spreading GOP voters efficiently across safe Republican districts.
Cracking is when the majority spreads the opposing party's supporters among multiple districts to dilute their influence. Packing is when a large number of voters from the opposing party are placed into a few districts to concentrate their votes.
The suit says in the 2014 state House elections, Democrats won statewide 51 percent to 49 percent but carried just 47 seats to the GOP's 63. It cites similar trends in the state Senate, where Republicans have a 27-11 edge, and the U.S. House, where the GOP has a 9-5 advantage.
Michigan's efficiency gaps, a way to measure whether gerrymandering has helped a political party enlarge its power, are the widest or among the largest in the country, according to the complaint.
A spokesman for Republican Secretary of State Ruth Johnson, the named defendant as Michigan's chief elections officer, declined to comment on pending litigation.
Michigan Republican Party spokeswoman Sarah Anderson said she could not comment on the content of the suit because she had not seen it, but added: "I would bet that it is about as credible as the recount lawsuit that Brewer filed for Jill Stein — that is, not at all."
Brewer, an election attorney, represented the Green Party candidate in her partial recount of Michigan's 2016 presidential election. The law firm where he works, Goodman Acker, is seeking donations toward the redistricting suit to cover the cost of non-lawyer expenses such as expert witnesses, filing fees and depositions.
"Ending partisan gerrymandering is critical to preserve our democracy and ensure every vote counts," said Sue Smith, director of the league's redistricting program.
This week, a group opposed to political gerrymandering submitted more than 425,000 signatures for a 2018 ballot drive to create an independent commission to draw Michigan's districts.