Washington (CNN) The Pennsylvania Supreme Court threw out the state's congressional map Monday, ruling that Republican-drawn districts "clearly, plainly and palpably" violate the state's constitution and ordering that the map be redrawn in the next three weeks.

The ruling could have a major impact on the race for control of the US House in 2018, where Democrats are targeting several Philadelphia-area House seats.

The League of Women Voters had challenged the district map in court, arguing that the state's congressional lines were "among the most extreme partisan gerrymanders in American history."

The group alleged that Republicans acted in secret in 2011 to design a map that deliberately packed Democratic voters into five districts, maximizing the GOP advantage everywhere else. Republicans currently hold 12 of Pennsylvania's 18 seats.

The court ruled that a new map must be submitted to Gov. Tom Wolf, a Democrat, by February 9 -- and then Wolf has until February 15 to accept it. If those deadlines are missed, the court said, it will draft a new map itself, with input from the parties.

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