Democratic voters suing to invalidate the current map of Pennsylvania’s congressional districts haven’t proven that it violates the state constitution by unfairly favoring Republican candidates, a judge said Friday.

Commonwealth Court Judge Kevin Brobson, a Republican, issued a 130-page report to the state Supreme Court by Friday’s deadline, set by the Democratic-majority high court that ordered the lower court to fast-track hearings and sum up the evidence.

The justices quickly scheduled oral arguments to be held Jan. 17.

Brobson wrote that the Democratic voters challenging the map had shown that the Legislature’s Republican majority leaders used partisan considerations when they drew the plan in 2011, and that it favored Republicans in some of Pennsylvania’s 18 congressional districts.

However, Brobson said the plaintiffs have not spelled out a standard for a court to determine whether the 2011 map “crosses the line between permissible partisan considerations and unconstitutional partisan gerrymandering under the Pennsylvania Constitution.”

Meanwhile, a separate lawsuit challenging Pennsylvania’s congressional map is pending in federal court in Philadelphia after a three-judge panel there heard arguments this month.

Time is ticking, since candidates for the 2018 can start circulating petitions Feb. 13 to get on the primary ballot, with a deadline of March 6 to submit the petitions.

The primary election is May 15, while a nationally watched special election in a southwestern Pennsylvania congressional district is being held March 13.

No congressional map in Pennsylvania has been struck down because of partisan gerrymandering claims, and the lawsuit, filed in June, was the first to challenge Pennsylvania’s 6-year-old congressional map. The lawsuit says Pennsylvania’s map is one of the worst gerrymanders in the country.

Pennsylvania’s 2011 map moved whole cities and counties into different districts and produced contorted district shapes that broke decades of precedent as Republicans sought to protect the delegation’s majority in a state with more registered Democratic voters.

Republicans now fill 13 of Pennsylvania’s 18 seats in the U.S. House, despite winning roughly half of the statewide congressional vote in the three ensuing congressional elections held after the map took effect.