Cynically, PA's (Republican-controlled) legislature have a vested interest in doing everything they can to make vote-by-mail as arduous and sketchy as possible.

Cynically, PA's (Republican-controlled) legislature have a vested interest in doing everything they can to make vote-by-mail as arduous and sketchy as possible. Disenfranchising voters in Philadelphia and its suburbs is the only way they stay in control of the state. We're literally seeing a race right now between the vote counters trying to finish the count and the leader of the Republican party suing to stop the count and invalidate as many mail-in votes as he can (because he knows they are likely to be overwhelmingly for his opponent).