March 7 was the first day for independent candidates, and the nominees of unqualified parties, to start petitioning in Pennsylvania. Those petitions are due on August 1. Although the statewide petitions are only 5,000 signatures, the district petitions are more severe, 2% of the winner’s vote in the last general election. For example, in the U.S. House 2nd district, the requirement is 6,451 signatures.
Therefore, it would be quite unsettling if the U.S. Supreme Court were to rule that the new districts should not be used, and the old districts should be used instead. All of the petitioning that has already occurred would be wasted effort. This is even more true for the primary petitions; the petitioning period for those petitions started in late February.
It is thought unlikely that the U.S. Supreme Court would upset the new districts, but it is conceivable. The Court still hasn’t ruled. The ruling could come at any time.