An Associated Press analysis finds that congressional districts drawn by Pennsylvania's Republican-controlled Legislature helped the GOP win nearly three more of the state's U.S. House seats in last year's election.
The analysis uses a formula called the efficiency gap, designed to detect cases in which one party may have secured power through political gerrymandering.
The courts have said gerrymandering can be unconstitutional, although there is no definitive answer to the question of how large an efficiency gap must be to indicate an unconstitutional gerrymander.
In a recent case challenging North Carolina's congressional districts, political scientist Simon Jackman suggested that an initial election efficiency gap of at least 7.5 percent in a state with more than 15 U.S. House districts should attract scrutiny. Pennsylvania fits that description.
