A decision to uphold the ruling, on the other hand, would send courts across the USA head-first into a legal thicket, where they would be asked to glean legislative intent in district-drawing and pore over electoral maps and data to discern evidence of imbalance.
According to University of Chicago Law professor Nick Stephanopoulos, four of the five most gerrymandered state legislative maps on partisan grounds in the last 45 years - as well as eight of the 10 statewide maps for the U.S. House of Representatives - were drawn since 2010. He said on Monday that Wisconsin's "redistricting process was entirely lawful and constitutional, and the district court should be reversed". There's extensive case law on racial gerrymanders, which has established that racial discrimination in districting is subject to strict scrutiny by courts.
"And so it's impossible to say whether or not something unfair happened or whether or not the plaintiffs in this case just want maps drawn to compensate for the natural disadvantage that Democratic voters have And if you do that, then aren't you making a partisan and political judgment that is just as much political as the one that the plaintiffs allege to have happened here", Esenberg asks.
Republicans who control the state legislature assured the court that they could draw new maps in time for the 2018 elections, if the court strikes down the districts.
Twelve Republican-dominated states are supporting Wisconsin in its defense of the 2011 redistricting plan.
Today the U.S. Supreme Court announced it will hear an appeal of the Wisconsin case Gill v. Whitford contending that the state legislative districts as drawn in the 2011 redistricting legislation, passed by the Republican controlled legislature and signed into law by Gov.
MSNBC's Pete Willams boils the case down to deciding "how much partisanship is too much". What was elusive, Kennedy said, was "a manageable standard by which to measure the effect of the apportionment and so to conclude that the state did impose a burden or restriction on the rights of a party's voters". This formula is now the subject of a federal lawsuit, Whitford v. Nichol, which has survived two motions, submitted by defenders of Wisconsin's Republican-drawn maps, that sought to kill the case.
Gerrymandering is the practice of one party packing as many voters of the other party into the fewest districts possible. They also say they have a natural edge in redistricting, since Democrats tend to cluster in cities and suburbs, creating districts that overwhelmingly vote Democratic. Gerrymanders work by forcing one party to "waste" votes. They call their metric the "efficiency gap", calculated by taking the difference between the number of "wasted votes" for each party, and dividing that difference by the total number of votes.
The Wisconsin court was not so definitive.
"Wisconsin's gerrymander was one of the most aggressive of the decade, locking in a large and implausibly stable majority for Republicans in what is otherwise a battleground state", said Thomas Wolf, redistricting counsel at the Brennan Center for Justice. Voters are either "cracked", pushed into districts where their party has no chance of winning; or "packed", crammed into districts where their party has such an overwhelming majority that additional votes for their candidate are superfluous. Any method of drawing districts will favor Republicans, they contend. It could alter the tradition of political parties redrawing voting districts for their political advantage. The Democratic plaintiffs in Wisconsin's case are hoping to change that.
Robert Barnes has been a Washington Post reporter and editor since 1987.
The key question, as always on this Supreme Court, is where Kennedy will land.