The last sub-q is easy. SCOTUS simply said:
The State of Texas’s motion for leave to file a bill of
complaint is denied for lack of standing under Article III of
the Constitution. Texas has not demonstrated a judicially
cognizable interest in the manner in which another State
conducts its elections. All other pending motions are dismissed
Statement of Justice Alito, with whom Justice Thomas joins:
In my view, we do not have discretion to deny the filing of a
bill of complaint in a case that falls within our original
jurisdiction. See Arizona v. California, 589 U. S. ___
(Feb. 24, 2020) (Thomas, J., dissenting). I would therefore
grant the motion to file the bill of complaint but would not
grant other relief, and I express no view on any other issue.
Basically, SCOTUS says that no US state ca sue another over how the latter runs its elections.
Now on the manner of changing balloting methods for Covid-19, this is a matter of what state law allows in each state. The legislature can delegate its powers for well-defined purposes. (This is how most government agencies exist.) Without getting into the minutiae of each state, organizing elections is typically delegated to the state election board. State laws may prescribe some elements for the election, but leave/delegate other elements to the board. It's not illegal for the board to make the decisions it is allowed to make by state law. For instance (besides arguing Texas had no standing) Pennyslvania's argument was also that
the alleged violations of state law were not, in fact, violations.
If you want to discuss specific states, ask for each separately. But to pick one example that was litigated from state courts all the way to SCOTUS--sort-of; the Kelly filing to SCOTUS actually did invoke the electors' clause. But first some background:
On November 22, 2020, U.S. Representative Mike Kelly and six other Republican representatives filed a suit in the Commonwealth Court of Pennsylvania that claims that the Pennsylvania General Assembly had no authority under the state constitution to enact no-excuse mail-in voting. [...]
The Pennsylvania Supreme Court ruled on November 28 to unanimously overturn the Commonwealth Court's order to block the certification of election results in Pennsylvania. The Pennsylvania Supreme Court also dismissed with prejudice the requests of the Republicans to either invalidate all 2.5 million mail-in ballots in Pennsylvania, or to invalidate all 6.9 million ballots in the state and have the state's Republican-controlled Legislature choose the presidential electors for the state. The rationale for the decision was that the Republicans were challenging the law too late; they had been able to challenge the law since it came into force in October 2019, but only filed the lawsuit when the results of the November 2020 election were "becoming seemingly apparent". Hence, the Republicans had failed to act with "due diligence" in their handling of the case.
Kelly appealed to the US Supreme Court. [...] On December 8, 2020 the Supreme Court rejected the request in a one-sentence, unsigned order; by the time of the high court's decision, the Pennsylvania election results had been certified in Biden's favor.
The sentence was merely:
The application for injunctive relief presented to Justice Alito and by him referred to the Court is denied.
Note here that in this latter case (Kelly) SCOTUS was acting in its appellate role, not in its original-jurisdiction role (as in Texas.) Furthermore, the Kelly filing to SCOTUS was on the basis that the law was unconstitutional under Pennsylvania's constitution and "thereby equally infringes on the powers granted to the Pennsylvania General Assembly under Article I, § 4, and Article II, § 1 of the U.S. Constitution." (A claim which SCOTUS basically disagreed with, without getting into any detail. Article II, § 1 is the electors' clause.)
Besides that Kelly case, there's another that has made its way to SCOTUS from Pennsylvania: Donald J. Trump for President, Inc. v. Boockvar. This one is actually still pending. It's actually a bit more properly on the matter of executive decision related to the election in Pennsylvania, as far as I can tell. The (267-page) filing in this case also opens with an invocation of Article II, § 1, so I'm guessing it alleges a violation electors' clause too, but it's a really long read... This case challenges not one but three different Pennsylvania Supreme Court decisions. Eventually, the petitioners claim that "The Three Decisions Violated Article II By Changing the Law During the Election."
On Jan 11, SCOTUS denied a "Motion to expedite consideration filed by petitioner", but otherwise the case is still pending. Boockvar's response (on Dec 30, only to the motion to expedite) was basically that
There is simply no dispute as to Pennsylvania’s electoral votes. But even if there were, it would be for Congress alone to resolve.
At least some of the press interpreted that SCOTUS decision to deny expedited consideration
as effectively denying Trump the remedy he sought, especially since the court did that on several suits at once:
The U.S. Supreme Court on Monday [Jan 11] said it would not speed up appeals challenging the 2020 presidential election results in Arizona, Georgia, Michigan, Pennsylvania and Wisconsin, effectively ending bids by President Donald Trump and his supporters to undo those states' results before President-elect Joe Biden's inauguration.
Monday's order list said without comment or dissent that the justices denied expedited consideration of petitions for review in seven suits across the five states, meaning the court would not fast-track its decision on whether to hear the cases — let alone decide them — before the constitutionally mandated end of Trump's term Jan. 20.
[...] The cases are Wood v. Raffensperger et al., case number 20-799; Ward v. Jackson et al., case number 20-809; Kelly et al. v. Pennsylvania et al., case number 20-810; King et al. v. Whitmer et al., case number 20-815; Donald J. Trump for President Inc. v. Boockvar et al., case number 20-845; Trump et al. v. Biden et al., case number 20-882; and Trump v. Wisconsin Elections Commission et al., case number 20-883; in the Supreme Court of the United States.
I'm not sure how may of those invoked the electors' clause, but I'm guessing most of them... I've spot checked the last (Wisconsin) case in that list, and it too invoked article II, § 1 in the synopsis I found.
As noted in another commentary it's possible that SCOTUS may [still] consider ruling on those cases in order to clarify the "game rules" for future elections.
Update: SCOTUS denied most of those cases on Feb 21-22; the last one in that list (the one from/against Wisconsin) was denied on March 8.
Supreme Court rejects Trump's final election challenge
The Supreme Court rejected former President Donald Trump's last remaining challenge of the 2020 presidential election on Monday, denying his request for them to hear his case against the Wisconsin Elections Commission.
Trump alleged that Wisconsin election officials violated state law by using what his attorneys called "unauthorized, illegal absentee voting drop boxes" and by allowing poll workers to correct absentee ballot witness certificates. Despite the election being over and President Biden already being in office, Trump continued to litigate the case, filing a brief in February arguing that the case was necessary to prevent similar situations in the future. [...]
The Supreme Court ultimately disagreed with this position, denying Trump's request for it to hear the case. The court's order came weeks after it denied several other election challenges, including a challenge of a Pennsylvania state court ruling that extended the deadline for accepting absentee ballots.
I think all of those SCOTUS decisions to deny petition were without detailed reasoning provided in the decision, as that's usually the norm.
However, in the batch of cases denied on Feb 21-22, there were some dissenting opinions recorded; Justices Alito, Gorsuch, and Thomas wrote a 15-page dissent between the three of them, albeit Thomas wrote a separate (11-page) one from the other two justices, who wrote a joint (4-page) one, so I'll have to be a bit selective based on the news reporting:
Justice Clarence Thomas called the cases an “ideal opportunity” to address an important question whether state lawmakers or state courts get the last word about the manner in which federal elections are carried out. And he called it “befuddling” and “inexplicable” that his colleagues were declining to weigh in.
“We failed to settle this dispute before the election, and thus provide clear rules. Now we again fail to provide clear rules for future elections. The decision to leave election law hidden beneath a shroud of doubt is baffling. By doing nothing, we invite further confusion and erosion of voter confidence,” he wrote. [...]
In addition to Thomas, two other justices — Samuel Alito and Neil Gorsuch — agreed. [...] “A decision in these cases would not have any implications regarding the 2020 election...But a decision would provide invaluable guidance for future elections,” Alito wrote. [...]
As is typical, neither Kavanaugh nor Barrett, each of whom might have provided a fourth vote needed for the court to take the case, wrote to explain why they declined to hear the case.