The U.S. Supreme Court on Monday allowed redistricting of Pennsylvania's congressional map to continue, denying a request from state Republican leaders to delay the process.

On Jan. 22, the Pennsylvania Supreme Court held that the state's current congressional map was the result of partisan gerrymandering and ordered lawmakers to redraw the districts in time for the primary election in May.

On Jan. 25, the two lead defendants in the case, state Senate President Pro Tempore Joe Scarnati and Speaker of the Pennsylvania House of Representatives Michael Turzai, filed an appeal to the U.S. Supreme Court asking that the justices stay the state Supreme Court's decision.

Justice Samuel Alito denied the request Monday.

The lawsuit challenging the congressional map was filed in the Commonwealth Court by the League of Women Voters and a group of Democratic voters against the state, questioning the fairness of the boundaries that make up Pennsylvania's 18th Congressional District. They claimed that the Republican-controlled Legislature manipulates districts in such a way as to minimize the impact of the state's Democratic voting population.

The U.S. Supreme Court's ruling could be a boon to Democrats in the upcoming 2018 midterm elections as they try to shift the balance of power in Congress.

“We're certainly very pleased, this was always a frivolous application because it was always a matter of state law,” said Mimi McKenzie of the Public Interest Law Center, who represents the League.

“We look forward to getting a fair, constitutional map in the next few weeks for Pennsylvania voters,” she added.

It is unclear at this time whether the legislators involved in the case plan to seek a full appeal of the state Supreme Court's ruling.

Jason Torchinsky of Holtzman Vogel Josefiak Torchinsky in Warrenton, Virginia, handled the lawmakers' U.S. Supreme Court filings and did not return a call seeking comment.

The Pennsylvania justices provided specific instructions for how the map is to be redrawn, noting that districts must be “composed of compact and contiguous territory; as nearly equal in population as practicable; and which do not divide any county, city, incorporated town, borough, township, or ward, except where necessary to ensure equality of population.”

Justice Max Baer, a Democrat, agreed with his colleagues' decision that the current map was unconstitutional, but expressed concerns that implementing the new map in time for the 2018 primary in May would cause confusion.

“It is naive to think that disruption will not occur,” Baer wrote in his opinion. “Prospective candidates, incumbents and challengers alike, have been running for months, organizing, fundraising, seeking their party's endorsements, determining who should be on canvassing and telephone lists, as well as undertaking the innumerable other tasks implicit in any campaign—all with a precise understanding of the districts within which they are to run, which have been in place since 2011.”

He continued, “The change of the districts' boundary lines at this time could result in candidates, again incumbents and challengers alike, no longer living in the districts where they have been carrying out these activities for a year or more.”

Chief Justice Thomas G. Saylor disagreed with the majority's ruling, as did Justice Sallie Updyke Mundy. Both are Republicans.