A panel of federal judges late Tuesday turned down a request by Pennsylvania Republican lawmakers to dismiss a lawsuit challenging the state's congressional district map. The ruling, hours after the three judges heard oral arguments in Philadelphia, means the case can proceed to trial next month.

The suit, Agre v. Wolf, is one of several claims nationwide that accuse lawmakers of intentionally drawing maps to ensure their party's victory. The Pennsylvania case seeks to have the map declared unconstitutional under a partisan gerrymandering theory relatively untested in the courts: The Elections Clause of the U.S. Constitution allows states to make decisions regarding voting, but not to insert partisanship when they do so.

That clause "does not confer upon the state legislature the authority to pick winners and losers in congressional elections," Thomas H. Geoghegan, a lawyer for the five Pennsylvania plaintiffs, argued during Tuesday's hearing.

Jason B. Torchinsky, a lawyer for House Speaker Mike Turzai and Senate President Pro Tempore Joe Scarnati, told the judges that the map drawn in 2011 was lawful and that "courts have recognized for generations that politics are part of the redistricting process."

Pennsylvania's current congressional map is considered by experts one of the country's most gerrymandered. Since its adoption, Republicans have won 13 of 18 congressional seats, even as voters statewide have been nearly split between Republicans and Democrats.

Less than two hours after the hearing, U.S. Circuit Judges D. Brooks Smith and Patty Shwartz and District Judge Michael M. Baylson issued a one-page order that the suit's Elections Clause claim can continue. They threw out two additional claims challenging the map.

It was the second time the suit had survived such a challenge. On Friday, U.S. Supreme Court Justice Samuel Alito denied a request for a stay.