HARRISBURG, Pa. (AP) — Pennsylvania’s high court imposed a new congressional district map for the state’s 2018 elections on Monday, potentially giving Democrats a boost in their quest to capture control of the U.S. House unless Republicans can stop it in federal court.

The map of Pennsylvania’s 18 congressional districts is to be in effect for the May 15 primary and substantially overhauls a Republican-drawn congressional map widely viewed as among the nation’s most gerrymandered. The map was approved in a 4-3 decision, with four Democratic justices backing it and one Democratic justice siding with two Republicans against it.

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The divided court appears to have drawn its own map with the help of a Stanford University law professor, although some district designs are similar to proposals submitted to the court by Democrats.

Most significantly, the new map gives Democrats a better shot at winning a couple more seats, particularly in Philadelphia’s heavily populated and moderate suburbs. There, Republicans have held seats in bizarrely contorted districts, including one labeled “Goofy Kicking Donald Duck.”

Democrats cheered the new map, which could dramatically change the predominantly Republican, all-male delegation elected on a 6-year-old map. The new map repackages districts that had been stretched nearly halfway across Pennsylvania and reunifies Democratic-heavy cities that had been split by Republican map drawers.

“It remedies the outrageous gerrymander of 2011, and that’s the important thing, that the gerrymander be over,” said David Landau, the Democratic Party chairman of Delaware County, which was ground zero for the “Goofy Kicking Donald Duck” district. “All that zigging and zagging is all gone, and it makes Delaware County a competitive seat now.”

Republican lawmakers said they will quickly challenge the map in federal court, arguing that legislatures and governors, not courts, have the constitutional responsibility to draw congressional maps.

Mark Harris, a Pittsburgh-based GOP campaign consultant, was one of many Republicans bashing the new product.

“It’s a straight Democratic gerrymander by a Democratic Supreme Court to help Democrats,” Harris said.

Independent analysts said the map should improve Democratic prospects while still favoring Republicans as a whole. An analysis conducted through PlanScore.org concluded the court’s redrawn map eliminates “much of the partisan skew” favoring Republicans on the old Republican-drawn map, although not all of it.

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University of Florida political science doctoral student Brian Amos said Democrat Hillary Clinton beat Republican Donald Trump in eight of 18 districts in the 2016 presidential election on the court’s map. That compared with six of 18 districts Clinton won in 2016 under the invalidated map.

The Democratic-majority state Supreme Court ruled last month in a party line decision that the district boundaries unconstitutionally put partisan interests above neutral line-drawing criteria, such as keeping districts compact and eliminating municipal and county divisions.

It’s the first time a state court threw out congressional boundaries in a partisan gerrymandering case, this one brought by registered Democratic voters and the League of Women Voters last June.

Republicans appear to face an uphill battle in federal court.

Michael Morley, a constitutional law professor at Barry University in Florida, said federal courts are normally reluctant to undo a state court decision.

“I think it will be a major obstacle and a major challenge to get around it,” Morley said.

Pennsylvania’s Republican delegation has provided a crucial pillar of support for Republican control of the U.S. House since 2010.

Republicans who controlled the Legislature and the governor’s office after the 2010 census crafted the now-invalidated map to elect Republicans and succeeded in that aim: Republicans won 13 of 18 seats in three straight elections even though Pennsylvania’s registered Democratic voters outnumber Republicans.

Meanwhile, sitting congressmen, dozens of would-be candidates and millions of voters were beginning to sort out which district they live in barely a month before the candidates’ deadline to submit paperwork to run.

Some races are wide open: There are six incumbents elected in 2016 not running again, the most in four decades. The new map also has immediate implications for some incumbents.

Republican Rep. Ryan Costello, whose suburban Philadelphia district was narrowly won by Clinton in 2016, is in even more dire straits now that his district adds the heavily Democratic city of Reading.

The map also removes the heart of one district from Philadelphia, where a crowd of candidates had assembled to replace the retiring Democratic Rep. Bob Brady, and moves it to suburban Montgomery County.

The new map does not apply to the March 13 special congressional election in the 18th District to fill the remaining 10 months in the term of former Republican Rep. Tim Murphy, who resigned amid an abortion scandal. But the winner will have a short stay in the seat unless they move: the court’s map puts both candidates’ homes in districts with a Pittsburgh-area incumbent.