After the 2010 census, the Wisconsin Legislature’s Republican leadership asked an outside attorney to advise it on redrawing district maps. The lawyer, hired at taxpayers’ expense, did his work in a private map room, which Republicans could enter only if they signed a confidentiality agreement. That offer didn’t extend to Democrats, who first saw the proposed changes when they were formally introduced. The new maps were adopted by the Republican-controlled state senate and assembly days after being made public.

In July attorneys sued on behalf of 12 Wisconsin voters who claim that the redistricting, which was in effect for the 2012 presidential election and the 2014 midterm, was unfairly partisan. The case is rooted in a 2014 paper co-written by Nicholas Stephanopoulos, an assistant professor at the University of Chicago Law School, that examined almost every redistricting since 1972. Stephanopoulos, who’s one of the lawyers on the Wisconsin case, tried to quantify the results. Gerrymandering generally follows one of two patterns: packing, the cramming of one party’s voters into a single district; and cracking, spreading a party’s voters across many districts to deny them the chance of reaching a majority.

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