Pennsylvanias highest court could be on the verge of setting unprecedented limits on how much politicians can redraw electoral districts to their party's advantage, a decision that would have profound legal and political consequences both in the state and the rest of the country.

The Pennsylvania Supreme Court will hear oral argument on Wednesday in a case alleging the states 2011 congressional map, drawn by Republicans, violates protections on freedom of expression and equal protection in the state constitution.

Since 2012, Republicans have consistently been able to win 13 of the states 18 congressional seats, despite winning only about 50 percent of the statewide vote. The Brennan Center for Justice describes the states congressional map as one of the worst partisan gerrymanders in the country, and an analysis by The Associated Press found that the map was responsible for an additional three GOP seats in Congress.

A ruling striking down the map would be deeply significant. Before the end of January, the Pennsylvania Supreme Court could order state lawmakers to redraw the congressional map ahead of the 2018 elections, giving Democrats a better chance of picking up GOP seats. The state court will have final say in this case, but the ruling comes as the U.S. Supreme Court considers similar federal cases and could also strike down electoral maps as too partisan and implement standards to determine when partisan redistricting goes too far something it has never done.

Michael Li, senior counsel at the Brennan Centers democracy program, said the Pennsylvania case could be one of the biggest blockbuster cases of 2018 - both politically and legally.

A win in Pennsylvania would suggest that advocates maybe have been overlooking state constitutions many of which, like Pennsylvanias, have more expansive and robust rights and protections than the federal constitution, Li wrote in an email. A win in Pennsylvania could open the door to more state court litigation.

While a ruling from the Pennsylvania Supreme Court would only affect the congressional map in the state, courts in other places will pay attention to Pennsylvanias ruling, said Lisa Marshall Manheim, a law professor at the University of Washington.

State courts often look to the decisions reached by other state courts for guidance when determining how to interpret their own constitutions and laws. If the Pennsylvania Supreme Court issues a forceful ruling against partisan gerrymandering, that precedent may help to inspire similar rulings in other states, Manheim said in an email.

Other courts may be particularly interested in this case given how difficult it has been for courts to develop standards for judging political-gerrymandering claims, she continued. If the Pennsylvania Supreme Court can identify and apply a workable legal framework, that will provide an important precedent for other courts and litigants to consider.

Democratic voters in each of Pennsylvanias 18 congressional districts are plaintiffs in the case now before the states Supreme Court. They claim that Republicans effectively punished them for their past votes for Democratic candidates by drawing the congressional map in a way that disadvantages Democrats. They argue that the map also violates the state constitutions guarantee of equal protection because it discriminates against Democratic voters. Lawyers for the plaintiffs wrote in an opening brief to the Pennsylvania Supreme Court that the congressional map is impervious to the will of voters.

The Republican defendants, led by state House Speaker Michael Turzai and Senate President Pro Tempore Joseph Scarnati, argue theres no evidence the Democrats challenging the map have been punished. They say that the congressional map on its own doesnt prevent the Democrats from getting access to constituent services or voting or expressing support for the candidate they want. Drawing electoral maps, they say, is always going to be intertwined with politics, and courts have never intervened to set a standard for how much politics can factor into redrawing district lines.

Courts have been extremely hesitant to step in and strike down electoral maps drawn by lawmakers, questioning whether controversies over redistricting are even controversies courts can resolve. At the federal level, a three-judge panel ruled in 2016 that the map for Wisconsins state legislative districts benefited Republicans enough to violate the U.S. Constitution. In North Carolina, a panel of federal judges issued a similar ruling last week, striking down the states congressional map. The U.S. Supreme Court heard oral argument in the Wisconsin case in October and it is currently considering whether it will take up the North Carolina case. This term, the Supreme Court will also hear a First Amendment challenge to Marylands congressional map, which benefits Democrats.

"While U.S. Supreme Court caselaw has been widely inconsistent in how to approach these claims, state constitutions offer more affirmative and explicit protections for the right to vote than the U.S. Constitution and can serve as a basis for attacking an unfair plan," Franita Tolson, a law professor at the University of Southern California, said in an email. She added that if the U.S. Supreme Court were to stay out of the fray over redistricting, state litigation would become an "even more important vehicle to fight gerrymandering."If the Pennsylvania court were to also stay out of the fray, Tolson said, it would make it even more difficult to fight partisan gerrymandering across the country.

When the plaintiffs in Pennsylvania originally filed their lawsuit, the states lower Commonwealth Court put the case on hold, pending the outcome of the U.S. Supreme Courts decision in the Wisconsin case. The plaintiffs appealed to the Pennsylvania Supreme Court, which agreed to hear it on an emergency expedited basis a signal that the court, where Democrats have a majority, could be eager to weigh in.

At the request of the Pennsylvania Supreme Court, Commonwealth Court Judge P. Kevin Brobson presided over the case in December. In his recommendation to the higher court, Brobson agreed that Republicans took partisanship into account during redistricting and said it was possible to use only neutral criteria to draw a map less favorable to the GOP.

However, Brobson also said that those challenging the map failed to give the court a standard by which it could judge partisan gerrymandering.

While petitioners characterize the level of partisanship evident in the 2011 plan as excessive and unfair, Petitioners have not articulated a judicially manageable standard between permissible partisan considerations and unconstitutional partisan gerrymandering under the Pennsylvania Constitution, he wrote.