There appears to be some misunderstanding regarding the possible scope of the Pennsylvania case that is before the SCOTUS. In
The Revenge of Clarence Thomas -- Bush v. Gore and the Facts Underlying The Pennsylvania Court Cases
Shipwreckedcrew does an admirable job of setting the record straight in that regard. You can read the whole Who-Struck-John of the case by following the link--and I encourage you to do so. The election likely hinges on Pennsylvania, so it's important to firmly grasp the issues. Here, I'll skip most of the factual basis in Bush v. Gore, referring readers to SWC. Instead, I'll try to offer a brief summary that highlights the two issues involved.
Yes, there are TWO issues. Most readers will be familiar with one of the issues--the question of whether the PA Supreme Court acted unconstitutionally in changing PA's election law--but there's a related issue we need to be aware of. Both the issues cropped up in Bush v. Gore in Florida.
In his presentation SWC leaves the more familiar issue to the end, but I'll put it up front.
That issue is, in the context of Bush v. Gore, referred to as the "Article II" issue. The reason is because Article of the US Constitution gives state legislature's the authority to determine the time and manner for holding presidential elections. Here's the Wikipedia summary:
Bush also argued that the Florida Supreme Court's ruling violated Article II, § 1, cl. 2 of the U.S. Constitution. Essentially, Bush argued that the Florida Supreme Court's interpretation of Florida law was so erroneous that its ruling had the effect of making new law. Since this "new law" had not been directed by the Florida legislature, it violated Article II. Bush argued that Article II gives the federal judiciary the power to interpret state election law in presidential elections to ensure that the intent of the state legislature is followed.
So what CJ Rehnquist argued was this: Normally the SCOTUS wouldn't interfere with a state supreme court's interpretation of its own state laws. However, in the case of a presidential election the state's authority to determine the manner of the election is granted by the US Constitution. Therefore, the federal courts are have the authority to review the state courts' interpretations of those state laws, because they derive from the US Constitution and implicate federal interests. In Bush v. Gore, Rehnquist argued that the Florida supreme court's interpretation was so drastic as to amount to a rewrite of Florida law--and that's exactly what Trump is arguing happened in Pennsylvania.
SWC believes that Trump has an excellent chance of prevailing:
The left-wing legal pundits have long treated the Rehnquist concurrence dismissively because only two of the other eight members of the Court joined the Chief Justice in his “textualist” approach to the meaning of “legislature” in Cl.2. On that same basis, they are treating the Petition to invalidate the Pennsylvania Supreme Court’s order that extended the ballot-receipt deadline — which raises the argument made by Chief Justice Rehnquist in concurrence — with similar dismissiveness. ...
But, what is important to know now is that Justice Thomas was one of the two Justices who joined Chief Justice Rehnquist’s concurrence. Further, the “textualist” view of Constitutional law has gained much ground in the judiciary since 2000. Justices Gorsuch and Barrett are clearly “textualists” in their approach to statutory and constitutional interpretation, and while not quite as clearly defined, Justice Kavanaugh has already written that he has significant issues with what the Pennsylvania Supreme Court did.
If Chief Justice Roberts lines up with the three liberals, and there is a 5-4 vote to overturn the Pennsylvania Supreme Court’s decision, the senior Justice in the majority determines who writes the Court’s Opinion. That would be Justice Thomas, and it is my prediction that in that event he would choose to write the opinion himself.
Some have argued that, since the main provision of the PA court's rewrite was an extension of the time period for accepting mail-in ballots beyond the deadline specified by the legislature, only about 10,000 ballots would be affected. However, the second issue potentially goes far beyond that.
The second issue flows from the Article II issue. This issue is one of Equal Protection under the US Constitution. Trump is arguing that Pennsylvania, by ignoring several very clear provisions of Pennsylvania law, has set up a two tier system that privileges some voters over others--in other words, all voters do not receive equal protection under the PA court's version of the law.
Now, in Bush v. Gore, what happened was that the Florida Supreme Court had ordered a state-wide recount. The problem with that, according to Bush, was that there was no state-wide standard for conducting such a recount:
Bush argued that recounts in Florida violated the Equal Protection Clause because Florida did not have a statewide vote recount standard. Each county was on its own to determine whether a given ballot was an acceptable one. Two voters could have marked their ballots in an identical manner, but the ballot in one county would be counted while the ballot in a different county would be rejected, because of the conflicting manual recount standards.
The result would be that voters in counties with a lenient standard for hand recounts would be "more equal" or privileged as compared to voters in counties with a stricter standard. So, a violation of the equal protection clause of the US Constitution.
The situation in Pennsylvania is a bit different, in that the classes of voters receiving disparate treatment is not based on geography--different standards in different counties. Instead, Trump is arguing that Pennsylvania has unconstitutionally set up two distinct and state-wide classes of voters, with each class receiving disparate treatment: Mail-in voters v. In Person voters. For various reasons--reasons that go beyond the three day extension--Trump is arguing that Mail-in voters are being privileged over In Person voters, in violation of the Equal Protection clause. And this has been done by disregarding the election law that was put in place by the PA legislature. It doesn't take much reflection to realize that this Equal Protection argument could have a far broader reach than the extra three days allowed for voting.
SWC's conclusion regarding the Equal Protection issue?
Contrary to the left-wing pundits, this action has a substantial likelihood of being favorably resolved in favor of the Trump campaign.