(Reuters) - The U.S. Supreme Court on Monday refused to block a lower court ruling requiring Republican-drawn congressional districts in Pennsylvania to be reworked immediately, boosting Democratic hopes of winning control this year of the U.S. House of Representatives.

Light from the setting sun shines on the Supreme Court in Washington, U.S., January 20, 2018. REUTERS/Joshua Roberts/File Photo

Justice Samuel Alito denied an emergency application filed by Republicans to stop the immediate reworking of the electoral district boundaries, preserving a ruling by the state’s top court that they had unlawfully sought partisan advantage over the Democrats in drawing the maps.

The Jan. 22 Pennsylvania Supreme Court ruling gives Republican legislators until Friday to submit a revised map to Democratic Governor Tom Wolf, who would have until Feb. 15 to sign off on the changes. If those deadlines pass without an agreement, the state court said it would rewrite the map itself.

In a statement, the state’s top Republican lawmakers, Senate President Pro Tempore Joe Scarnati and House Speaker Mike Turzai, said they still believe the Pennsylvania Supreme Court exceeded its authority.

“We will do our best to comply with the Pennsylvania Supreme Court’s Jan. 22 order, but may be compelled to pursue further legal action in federal court,” they said.

A new map potentially could give Democratic candidates a chance to pick up several Republican-held seats in Pennsylvania alone, with national polls showing voters strongly favoring Democrats in 2018 over President Donald Trump’s party.

Democrats, who hold only five of Pennsylvania’s 18 congressional districts despite its status as a closely divided electoral swing state, must capture at least two dozen seats currently held by Republicans in the Nov. 6 congressional mid-term elections to wrest control of the U.S. House.

The Pennsylvania fight is one of several across the United States focusing on what is known as partisan gerrymandering, the manipulation of the composition of legislative districts to amplify the voting power of one party at the expense of another.

In a 5-2 vote along party lines, the Democratic-controlled Pennsylvania court ruled that Republicans crafted the map to deprive Democratic voters of meaningful ballots, violating the state Constitution’s guarantees of equal protection and free speech.

CHAOS PREDICTED

Republicans, including members of the state legislature, potential candidates and voters, asked the Supreme Court to put the ruling on hold, saying redrawing the district lines this month would cause chaos ahead of the November House races.

Experts have held up Pennsylvania as one of the most extreme examples of gerrymandering, pointing to bizarrely shaped districts that have earned nicknames like “Goofy kicking Donald Duck.” The Republican-controlled legislature created the current map in 2011, after the 2010 U.S. census.

The appeal had been seen as a legal long shot in part because the underlying lawsuit was based on the state Constitution, not the U.S. Constitution.

The legal challenge was brought by the League of Women Voters of Pennsylvania and several Democratic voters.

“This was always a Pennsylvania state court case about Pennsylvania’s Constitution, and the U.S. Supreme Court rightly refused the Republican legislative leaders’ attempt to manufacture a federal issue,” said R. Stanton Jones, a lawyer for the plaintiffs. “Pennsylvania voters will now get to cast their ballots in fair elections this year.”

The U.S. Supreme Court is already weighing whether to set for the first time a legal standard for partisan gerrymandering in two cases out of Wisconsin and Maryland. The court is expected to rule by the end of June in both cases.

In an action that could help Republicans keep control of the House, the high court on Jan. 18 put on hold a Jan. 9 federal court ruling that had ordered Republican-draw congressional districts in North Carolina to be redrawn because of partisan gerrymandering.