Thursday is deadline day in Pennsylvania’s high-stakes gerrymandering case for Democratic Gov. Tom Wolf and others to submit maps of new congressional district boundaries that they want the state Supreme Court to adopt for this year’s election.

The midnight deadline gives justices four more days to impose new boundaries, under a timeline the divided court set to keep May’s primary election on schedule.

Pennsylvania’s congressional map is widely viewed as among the nation’s most gerrymandered. Upending it could boost Democrats nationally in their quest to capture control of the U.S. House and dramatically change the state’s predominantly Republican, all-male delegation. Meanwhile, sitting congressmen, dozens of would-be candidates and millions of voters could find themselves in different districts.

Republican lawmakers say they will swiftly ask federal judges to block a new map, and contend that the Democratic-majority court had no power to invalidate the congressional boundaries or draw new ones.

Wolf and several other parties — including the registered Democratic voters who sued to invalidate the map — can each submit as many suggested maps as they like. The court will be advised by Stanford University law professor Nathan Persily, who has assisted judges drawing districts in North Carolina, New York, Connecticut, Georgia and Maryland. The justices could pick a submitted map, or rely on Persily to draw one.

Leaders of the state Legislature’s huge Republican majorities submitted a map Friday, although Wolf rejected it, saying it was as gerrymandered as the 6-year-old map it would replace.

Pennsylvania’s congressional map is widely viewed as among the nation’s most gerrymandered.

That map, crafted by Republicans who controlled the Legislature and governor’s office after the 2010 census, was drawn to help Republicans get elected. They succeeded: Republicans won 13 of 18 seats in three straight elections, even though Pennsylvania’s statewide elections are often closely divided and registered Democratic voters outnumber Republicans.

In drawing it, Republicans broke decades of precedent and created bizarrely shaped districts in what Franklin and Marshall College political scientist G. Terry Madonna called “the worst gerrymander in modern Pennsylvania history.”

The court threw it out last month, saying it unconstitutionally put partisan interests above other line-drawing criteria, such as eliminating municipal and county divisions and keeping districts compact.

The revised map Republicans submitted reduced splits and ironed out some of the most contorted boundaries. It also kept nearly 70 percent of residents — and every congressman — in their old districts in what Republicans called an effort to minimize disruption, although it shifted key Democratic challengers into new districts and Wolf criticized it as keeping “nearly 70 percent of residents in districts the court found unconstitutional.”

The court gave no direction to protect incumbent lawmakers or to keep previous districts largely intact. Meanwhile, the NAACP wrote to Wolf and top lawmakers last week to warn against redrawing two Philadelphia-based districts to “disenfranchise the vast and robust communities of color.”

READ MORE: In blow to GOP, Supreme Court won’t block Pennsylvania redistricting