The Michigan capitol buildingRebecca Cook / Reuters

A panel of federal judges in Michigan on Thursday unanimously struck down nearly 30 of the state’s U.S. House and state legislative districts as unconstitutional. Furthermore, the court ordered special early elections for several state-Senate seats—an unusual and aggressive remedy. It’s the latest in a string of rulings that show federal courts are more open to claims that partisan gerrymandering violates the U.S. Constitution, and more willing to employ strong measures to halt it.

It will be impossible to assess the full impact of the Michigan ruling until the U.S. Supreme Court issues its ruling on a pair of partisan-gerrymandering cases that it heard in March from Maryland and North Carolina. The high court has approached partisan-gerrymandering cases cautiously, punting a Wisconsin case back to a lower court to determine whether the plaintiffs had standing.

But while the justices hesitate, partisan gerrymandering has become a major issue in lower courts. Most of these cases spring from redistricting conducted after the 2010 census. That year, Republicans dominated state legislative elections, and using their new power drew maps that heavily favored GOP candidates. They were extremely effective. In 2018, for example, Republicans held on to majorities in the Michigan legislature despite Democrats winning the popular vote in legislative races. (Republicans note that Democrats also suffer from having their voters heavily concentrated in urban areas.)

Courts have long held that racial gerrymandering is unconstitutional, but they’ve been reluctant to rule against partisan gerrymandering, for fear of meddling in political matters. Where majority parties hold redistricting power, they have generally been given wide leeway to draw maps as they see fit. In the North Carolina gerrymandering case, Republicans who drew the maps have explained that they turned to partisanship as a method of drawing maps for fear of breaking the law on racial gerrymanders.

But new technologies have shifted the playing field. First, they allowed those doing redistricting to draw ever more ruthlessly efficient partisan gerrymanders. Second, they have allowed critics of those maps to use elaborate mathematical formulas to try to convince judges that partisan gerrymandering can be determined with more than mere subjectivity. Among the leading metrics are the “efficiency gap,” a method of calculating how many votes are wasted, and simulations that demonstrate the implausibility of existing maps.

Both of those metrics factored into the Michigan case. The plaintiffs also followed in the path of plaintiffs in the Maryland and North Carolina cases, arguing that the Michigan maps violated their First Amendment and Fourteenth Amendment rights. In the former case, they say their right to free association (in this case, with other Democrats) has been violated; in the latter, they say they are being governed in a way that violates their right to equal protection. The judges on the panel, including two Bill Clinton appointees and one George H. W. Bush appointee, agreed unanimously.

“[Republican mapmakers’] primary goal was to draw maps that advantaged Republicans, disadvantaged Democrats, and ensured that Republicans could enjoy durable majorities in Michigan’s congressional delegation and in both chambers of the Michigan legislature for the entire decade,” Judge Eric L. Clay, a circuit-court judge, wrote in the opinion. “The expert evidence, documentary evidence, and testimony from map-drawers, legislators, and political operatives undeniably points to this conclusion.”

This is not the first case in which a federal court has concluded that an unconstitutional partisan gerrymander exists, following the Wisconsin, Maryland, and North Carolina cases. But it is notable because of the order of early special elections. Courts have ordered new maps drawn, but have mostly avoided ordering new elections. A rare example came in a North Carolina racial-gerrymandering case, called Covington, in 2016, but the U.S. Supreme Court, while upholding their judgment, ordered them to reconsider the special election. The judges ultimately decided against it.

But in Michigan, the court considered the Supreme Court’s test for when a new election is merited in Covington and decided to order new elections for some legislative seats.

There’s a good chance that the Supreme Court will stay the Michigan ruling pending its decision on the Maryland and North Carolina cases, which are expected by the end of this term in June, Rick Hasen, an election-law expert at UC Irvine, told me. The Supreme Court’s conservative majority is expected to be skeptical of partisan-gerrymandering claims. But if the justices end up accepting either the First or Fourteenth Amendment rationales, the Michigan ruling would quickly take effect.

Time is of the essence in the outstanding partisan-gerrymandering cases. There will be a new census next year, and with it new redistricting around the country, so the window to correct any current injustices is closing.

But in Michigan, at least, there won’t be partisan gerrymanders coming out of the legislature after the 2020 census—no matter which party ends up in control in Lansing. In November, voters overwhelmingly passed a constitutional amendment that will take redistricting out of the hands of the legislature and grant it to a new, nonpartisan, independent commission.

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