WASHINGTON (AP) -- Democrats and Republicans are poised for a Supreme Court fight about political line-drawing with the potential to alter the balance of power across a country starkly divided between the two parties.
The big question at the heart of next week's high court clash is whether there can be too much politics in the inherently political task of drawing electoral districts. The Supreme Court has never struck down a districting plan because it was too political.
The test case comes from Wisconsin, where Democratic voters sued after Republicans drew political maps in 2011 that entrenched their hold on power in a state that is essentially evenly divided between Democrats and Republicans.
"It could portend massive changes in our electoral system," Washington lawyer Christopher Landau said, if the court for the first time imposes limits on extreme partisan gerrymandering, or redistricting. Courts have struck down racially discriminatory maps for decades.
Wisconsin Republicans controlled the redistricting process that followed the once-every-decade census because they held the governor's office and both houses of the legislature. They worked in secret to fashion precise, computer-generated maps and won approval on a party-line vote.
The results in three elections held under those maps have almost perfectly aligned with their predictions, even in 2012, when Democratic President Barack Obama carried the state. Democratic legislative candidates won a majority of the vote statewide then, but wound up as the minority party in the State Assembly.
"I don't want anybody, any party, to be in full control," said Emily Bunting, an organic farmer from western Wisconsin who joined the lawsuit. "I want fair elections, is what I want. I don't think a Democratic gerrymander is any better than a Republican one. I think that issue needs to be addressed."
A handful of Republican elected officials, including Sen. John McCain of Arizona and Gov. John Kasich of Ohio, have joined in the call for the court to rein in extreme partisan gerrymandering.
"From our vantage point, we see wasted votes and silenced voices. We see hidden power. And we see a correctable problem," McCain and Democratic Sen. Sheldon Whitehouse said in a Supreme Court brief.
But the parties are otherwise sharply divided, with Republicans arguing that courts should not be involved in the competition between the parties to wring gains out of redrawn electoral maps. Texas Solicitor General Scott Keller told the justices that "political competition is a necessary component of legislative-controlled redistricting."
A three-judge court in Wisconsin, though, agreed with the Democratic voters that there was too much politics in the Wisconsin maps. The redistricting packed Democratic voters into some districts and scattered them across others, with the aim of limiting how many seats Democratic candidates could carry, even in a good year for Democrats.
The case will be argued before the nine justices on Tuesday, although the arguments will be tailored to just one, Anthony Kennedy.
People on both sides of the case widely anticipate that the four liberal justices will side with the voters who sued. Conversely, the four conservatives probably will think these disputes should be resolved by the political branches, not the courts.
That leaves Kennedy, who has left the door open to court challenges to extreme partisan redistricting, but has never found a satisfactory way to measure it.
The legal team representing the Democratic voters is saying, "'Justice Kennedy, we have found the shiny holy grail you said was lacking,'" Landau said. He was describing the test that the three-judge court used to establish the districting plan's discriminatory intent, its likely durability over its 10-year life and the inability to explain it other than for partisan advantage.
Gerald Hebert, who directs voting rights and redistricting litigation at the Campaign Legal Center, said the case his team is making is not a partisan one, even though the center represents Democrats in the case.
"If we're going to get Justice Kennedy's attention, we have to make sure he really understands this is not just a Democratic problem. It happens to be right now that Republicans control way more legislatures. But ... in states where Democrats control the entire redistricting process, the districts also are gerrymandered," Hebert said.
Other lawsuits challenging maps are ongoing in Maryland, where Democrats hold all but one of the state's eight seats in the House of Representatives, and North Carolina, another narrowly divided state in which Republicans nonetheless hold commanding majorities in the legislature and the state's congressional delegation.
Defending the maps in the Supreme Court case, Wisconsin Attorney General Brad Schimel, a Republican, said courts would be overwhelmed with partisan redistricting lawsuits if the high court rules against the state.
"The Supreme Court has never permitted a map to be struck down when you followed traditional redistricting criteria and these maps do," Schimel said.
Thirty-one years ago, in an earlier case about partisan redistricting, it was the Republican National Committee that pointed to the dangers when one party held too much sway over map-making.
"The new technology available to redistricters provides those in the majority with a very tempting means of discriminating against any minority, political or otherwise," the RNC wrote, concluding that "the vitality of America's political parties, and the integrity of our representational government, are at stake."