By Lawrence Hurley and Andrew Chung
WASHINGTON (Reuters) - U.S. Supreme Court justices on Wednesday appeared conflicted over what to do -- if anything -- to rein in politicians who draw state electoral maps with the aim of entrenching their party in power in a closely watched case from Maryland over the practice known as partisan gerrymandering.
The nine justices heard an hour-long argument in a challenge by Republican voters to a U.S. House of Representatives district in Maryland that was reconfigured by Democratic state legislators in a way that helped the Democrats defeat an incumbent Republican congressman.
There appeared little dispute among the justices that the Maryland district's lines were drawn with partisan intent.
But based on questions they asked, the justices seemed no closer to answering the major question in this case and a similar one involving Wisconsin: whether courts should be able to intervene to curb the manipulation of electoral district boundaries purely to favor one party over another.
On Oct. 3, the court, which has a 5-4 conservative majority, seemed similarly torn when it heard a challenge by Democratic voters to Republican-drawn legislative districts statewide in Wisconsin, and has not yet issued a ruling.
The rulings in the two cases, due by the end of June, could alter the U.S. political landscape, either by imposing limits on partisan gerrymandering or by allowing it even in its most extreme forms.
Opponents have said partisan gerrymandering has begun to warp American democracy by muffling large segments of the electorate.
Liberal Justice Stephen Breyer suggested the court delay deciding the cases and instead hear another round of arguments in its next term, starting in October, along with a similar case from North Carolina.
"It seems like a pretty clear violation of the Constitution in some form to have deliberate, extreme gerrymandering," Breyer said. " ... But is there a practical remedy that won't get judges involved in every -- or dozens and dozens and dozens of very important political decisions?"
Liberal Justice Elena Kagan agreed with Breyer about the problem of deciding the threshold for when partisan line-drawing becomes too much to allow, but said, "However much you think is too much, this case is too much."
"How much more evidence of partisan intent could we need?" Kagan asked.
The Maryland voters, supported by Republican Maryland Governor Larry Hogan, appealed a lower court ruling rejecting their challenge.
Conservative Justice Anthony Kennedy, a potential key vote in the case, raised concerns about a ruling so soon before November's mid-term election but also indicated there was evidence of partisan intent in Maryland.
Maryland's lawyer Steven Sullivan said the law enacting the state's electoral map contained no language suggesting partisan intent, prompting a sharp response from Kennedy.
"So if you hide the evidence of what you're doing, you're going to prevail?" Kennedy asked.
The Supreme Court for decades has invalidated state electoral maps due to racial discrimination but not due to partisan advantage.
Democrats have said partisan gerrymandering by Republicans in such states as Wisconsin and Pennsylvania has helped President Donald Trump's party maintain control of the House and various state legislatures.
Republican voters sued Maryland after the legislature in 2011 redrew boundaries for the state's Sixth District in a way that removed Republican-leaning areas and added Democratic-leaning areas. Democrat John Delaney subsequently beat incumbent Republican Roscoe Bartlett to take the seat in 2012.
Governor Hogan's election victory in 2014 illustrated Republican strength statewide. But Republicans hold just one of Maryland's eight House seats because of the way the districts are configured.
The question before the Supreme Court is whether Maryland's electoral map violated the U.S. Constitution's First Amendment guarantee of free speech. The novel legal theory pursued by the challengers is that Republican voters were retaliated against by Democrats based on their political views.
In a 2004 ruling in another case, Kennedy suggested that if partisan gerrymandering went too far courts might have to step in if a "workable standard" could be found.
Conservative Justice Samuel Alito on Wednesday told the Maryland plaintiffs' lawyer he did not think their First Amendment challenge offered a workable standard.
"I don't see how any legislature would ever be able to redistrict," Alito said.
The Wisconsin challengers presented a different argument, focusing on the Constitution's 14th Amendment guarantee of equal protection under the law because of the extent to which it marginalized Democratic voters.
Gerrymandered electoral maps often concentrate voters who tend to favor the minority party into a small number of districts to dilute their statewide clout and distribute the rest of those voters in other districts in numbers too small to be a majority.
Legislative districts are redrawn nationwide every decade to reflect population changes after the national census. Redistricting in most states is done by the party in power, though some states in the interest of fairness assign the task to independent commissions.
(Reporting by Lawrence Hurley and Andrew Chung; Editing by Will Dunham)