HARRISBURG — The Pennsylvania Supreme Court on Monday struck down the boundaries of the state’s 18 congressional districts, saying they violate the state constitution and granting a major victory to a group of Democratic voters who argued the districts were unconstitutionally gerrymandered to benefit Republicans.

The Democratic-controlled court issued a brief order giving 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 said they will adopt a plan in an effort to keep the May 15 primary election on track.

The 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 contorted shapes, including one dubbed “Goofy kicking Donald Duck.”

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.

The U.S. Supreme Court also is weighing whether redistricting can be so partisan that it violates the U.S. Constitution, in cases from Maryland and Wisconsin. The high court has never struck down an electoral map as a partisan gerrymander.