Those maps, drawn mainly in secret by Republican lawmakers, had achieved one of the clearest cases in modern political history of achieving a lasting advantage for Republican candidates, even though the state's voters are about evenly divided in their affiliation with the two major parties.
The U.S. Supreme Court will consider whether judges can throw out legislative maps as being so partisan they violate the Constitution, taking up a case that could put a powerful new check on gerrymandering.
While the precise schedule of Wisconsin's redistricting case is not yet known, experts say the court could hear oral arguments late this year or early next year, and a decision in the case is nearly sure to come by June 2018.
Enter the Wisconsin case.
Legislative boundaries get redrawn every decade after the U.S. Census to make sure they're equal in population, but when one party controls all of state government as Republicans did after the 2010 wave election, they can draw maps that give themselves a partisan edge.
The justices may have given an early sense for which way they're leaning, issuing an order halting a lower court's ruling that had demanded Wisconsin redraw its maps by November. Depending on the ruling, up to seven states' congressional maps could be affected - including Texas, according to Michael Li, redistricting and voting counsel at New York University's Brennan Center for Justice.
A Supreme Court ruling faulting the Wisconsin redistricting plan could have far-reaching consequences for the redrawing of electoral districts due after the 2020 USA census. "And by that metric, plaintiffs looked back at redistricting plans throughout the US, going back to 1972, and Wisconsin's redistricting plan was one of the most strongly political gerrymandered in history". In 2016, a federal district court agreed with those Democratic voters, ruling that the state's election map had been drawn for partisan advantage. Kenneth Ripple, the author of that opinion, wrote, "We conclude ... that the evidence establishes that one of the purposes of [the district map] was to secure Republican control of the Assembly under any likely future electoral scenario for the remainder of the decade, in other words to entrench the Republican Party in power". But Justice Anthony Kennedy, 80, would not go that far; he may be the swing vote in the new case - if he doesn't retire over the summer. Kennedy, writing in a 2004 case, indicated he may be open to the idea that racial gerrymanders could violate the Constitution. "No matter which side of the aisle you're on, we should all be able to agree on one thing: as voters in a democracy we should have the right to freely choose our representatives rather than endure a system where politicians manipulate our district lines, dilute our votes, and choose their own constituents". Republicans call their actions lawful.
A recent study from the Brennan Center found that gerrymandering has resulted in 16 or 17 additional Republican seats in Congress, or about two-thirds of the 24 seats Democrats would need to take over the House. By a vote of 5-4, the court also granted Wisconsin Attorney General Brad Schimel's application for a stay in the redistricting case, Gill v. Whitford. Under those maps in 2012, Republicans captured 61 percent of state assembly seats while winning 48.6 percent of the statewide vote. In 2014, the party garnered 52 percent of the vote and 63 state Assembly seats.
Last week, the League of Women Voters filed a lawsuit alleging that Pennsylvania's congressional district boundaries unfairly favor Republicans. Democratic voters are clustered in cities such as Milwaukee and Madison, while Republican voters are more evenly spread across the state.