An attorney for the group challenging Pennsylvania's congressional boundaries told a panel of federal judges Monday he would seek to show that they were unfairly drawn to favor Republicans through the use of sophisticated software and detailed datasets.

Lawyers for Republican state lawmakers countered that statewide election results shed no light on the individual districts, since voters elect members of Congress in their own districts and not statewide, and that politics has always been an accepted part of the redistricting process.

"We're in a new technical world here," said Thomas H. Geoghegan, a lawyer for the plaintiffs.

He spoke during opening statements in the first of two trials this month scrutinizing the fairness of Pennsylvania's congressional map. A similar challenge starts in state court next week. Both come as courts and communities nationwide have been wrestling with the issue of political gerrymandering, and how it can give one party an outsize  influence in government.

Going through the results of several elections, Geoghegan told the panel of three federal judges in Philadelphia that votes across the state have been roughly split between Democrats and Republicans.

But since since the 2011 map went into effect, Republicans have consistently won 13 of the state's 18 congressional districts.

Jason B. Torchinsky, a lawyer for House Speaker Mike Turzai and Senate President Pro Tempore Joe Scarnati, responded in his opening statement that elections are held in districts for individual candidates. He also argued that "political considerations are part and parcel of the redistricting process."

The voters bringing the suit, led by Louis Agre, a Democratic Ward leader who represents most of Roxborough and Manayunk, are invoking the Elections Clause of the U.S. Constitution, which they say gives states the power to run elections and make voting-related decisions, but not to insert partisanship when they do so.

So where other suits, including a case currently before the U.S. Supreme Court, seek to argue that a map goes too far as a gerrymander, this one seeks to say that any degree of gerrymandering is unlawful.

"We all know the uniqueness of this particular claim," said one of the judges on the panel, Michael J. Baylson. The judges have thrown out other, more traditional gerrymandering claims that the plaintiffs had hoped to make.

The judges heard from two witnesses Monday: Daniel McGlone, an analyst at Philadelphia-based mapping and geographic data analysis firm Azavea, and Anne Hanna, a doctoral student at Georgia Tech.

McGlone described the results of his analyses of the congressional map and election results, going through districts to show ways that they appeared to favor Republicans. Hanna ran through maps she had created using data, provided by Turzai, that was used during the redistricting process, to similarly show how they appeared to favor Republicans.

If the challenge is successful, it could force a redrawing of Pennsylvania's map before next year's midterm elections. In that case, a lawyer for Gov. Wolf and other state officials said, the state would work to accommodate that process, including adjusting primary dates and schedules.

More likely, the defendants would appeal the case to the U.S. Supreme Court, Michael Li, a gerrymandering expert at the Brennan Center for Justice at New York University, said in an interview Monday. And its resolution probably would be stayed pending the Supreme Court decision in a gerrymandering challenge brought in Wisconsin.

The lawsuit most likely to affect the Pennsylvania map before 2018, Li said, begins next week, when the state trial begins in League of Women Voters v. Pennsylvania.

One of the biggest obstacles for the plaintiffs in federal court will be that their case could invalidate many maps, Li said. Even maps drawn with politically neutral principles could happen to favor one party or another, even without intent.

"There's not really a question to whether Pennsylvania has a good map or a bad map. It clearly has a bad map," Li said. "The question is whether the legal theory opens the door to too many lawsuits."