It’s virtually undisputed that Pennsylvania’s congressional map satisfies this test. The map was drawn in secret by Republicans using reams of sophisticated data. It was then jammed through the General Assembly, largely on party-line votes, in a matter of days. In the 2012, 2014, and 2016 elections, the map set a modern record for partisan unfairness. According to one metric, it was more skewed, on average, than any other congressional map in the country since 1972.
This enormous Republican advantage is likely to endure for the rest of the decade. It would take a five-point swing for Democrats to capture just one more seat. For the map’s skew to disappear, Democrats would need to improve on their 2016 showing by 14 points — a bigger wave than Pennsylvania has seen in generations. And the map’s tilt can’t be explained by the clustering of Democratic voters in Philadelphia and Pittsburgh. In hundreds of computer-simulated maps, Democrats usually win nine or 10 of Pennsylvania’s 18 districts. The state’s underlying geography is thus close to neutral.