And THAT is the problem right there. That signature, and a PDF of the ballot, should be sent to the respective Registrar of voters as a vote confirmation. As it stands now, voters have no record of their actual votes.
That needs to change.
While SCOTUS could rule that the PA Supreme Court wrongfully interpreted PA statutory law, but it would be extremely rare, (almost impossible normally). Usually the court defers to state supreme courts and their interpretations of state law, and would be unlikely to grant certiorari to review such a determination. The district court judge will undoubtedly defer to that as well. However, Article II, sec. 1 of the U.S. Constitution grants the power to determine the selection of presidential electors exclusively to the state legislatures. So, SCOTUS can rule that the PA Supreme Court exceeded its authority in a presidential election. (I doubt a lower federal court would do this.) In this case, PA elects its judges, including the Supreme Court, and it would be possible to find that they are acting as partisans, not neutral and detached judges, especially when the court divides along party lines as it did here. (A determination like that from SCOTUS would be unlikely as it would undermine confidence in state courts.)
What the PA Democrat machine is doing is the kind of âÂÂcutesyâ thing that courts usually reject. The 14th Amendment equal protection clause is relevant as different counties allowed different levels of review for the mail in ballots. So, PA has 67 counties. If in 65 counties polling observers were able to inspect and challenge the signatures of mail in ballots, but in two, Philadelphia and Pittsburgh, they could not, then the equal protection clause was violated. Then the only issue is the proper remedy, i.e., invalidating ballots not permitted to have been viewed by poll watchers.
(Note: I attempted to post this once, and it appears to have failed. This is a repost with some editing.)