The map of congressional districts imposed by Pennsylvania's high court for the state's 2018 elections boosts Democrats in their mission to wrest control of the U.S. House.
Republicans have vowed to immediately challenge it in federal court, perhaps as early as Tuesday.
The map of Pennsylvania's 18 congressional districts takes effect for the May 15 primary and substantially overhauls a Republican-drawn congressional map widely viewed as among the nation's most gerrymandered.
New boundaries will usher in changes to Pennsylvania's predominantly Republican delegation.
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.
Meanwhile, candidates are finding themselves in a new landscape and rethinking campaigns a week before they can start circulating petitions to run.