HARRISBURG, Pa. -- The Pennsylvania Supreme Court has struck down the boundaries of the state's 18 congressional districts, granting a major victory to plaintiffs who had contended that they were unconstitutionally gerrymandered to benefit Republicans.

The Democratic-controlled court issued the order Monday. It gives the Republican-controlled Legislature until Feb. 9 to pass a replacement and Democratic Gov. Tom Wolf until Feb. 15 to submit it to the court. Otherwise, the justices say they will adopt a plan in an effort to keep the May 15 primary election on track.

The defendants - top Republican lawmakers - said they would ask the U.S. Supreme Court this week to step in and put the decision on hold. The state court's decision lacks clarity, precedent and respect for the constitution and would introduce chaos into the state's congressional races, they said.

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The Senate's top Republican lawyer, Drew Crompton, called the timeline to draw new districts "borderline unworkable," but said Republicans will do everything they can to comply.

The Pennsylvania top court court said the boundaries "clearly, plainly and palpably" violate the state's constitution, and blocked it from remaining in effect for the 2018 elections. The deadline to file paperwork to run in primaries for the seats is March 6.

Republicans who controlled the Legislature and governor's office following the 2010 census broke decades of geographical precedent when redrawing the map, producing one of the country's most gerrymandered districts outside Philadelphia, dubbed "Goofy kicking Donald Duck" for its absurd shape.

A map of Pennsylvania's gerrymandered 7th Congressional District, encompassing parts of five counties in the Philadelphia suburbs. CBS News

They shifted whole counties and cities into different districts in an effort to protect a Republican advantage in the congressional delegation. They succeeded, securing 13 of 18 seats in a state where registered Democratic voters outnumber Republicans 5 to 4.

"We won the whole thing," said David Gersch of the Arnold & Porter Kaye Scholer law firm in Washington, D.C., which is helping represent the group of registered Democrats who filed the lawsuit last June.

The decision has immediate implications for the 2018 election, meaning that 14 sitting members of Congress and dozens more people are running or considering running in districts they may no longer live in.

The March 13 special election in a vacant southwestern Pennsylvania seat is unaffected by the order, the justices said.

But it's not just Pennsylvania that deals with the manipulation of voting district lines. The issue of gerrymandering is before the Supreme Court right now, and a decision is expected this spring.