Regarding the Supreme Court's decision on a lack of standing for TX et Al. to challenge election practices in other States:

Article I, Section 10, Clause 3 of the USC states that States may not "keep troops or ships of war..." or "engage in war".  When the States entered into Union with one another, they relinquished the right to settle differences by force of arms.  If a dispute arose on the execution of Federal law within another State, there was no recourse but appeal to the Government, which falls squarely in Article III, Section 2.  To state it clearly, States gave up this sovereign right with the promise that the Supreme Court would adjudicate disputes.

For a modern example, consider the Ukraine.  After the fall of the Soviet Union, the Ukraine was an independent sovereign nation, armed with Nuclear Weapons.  In exchange for relinquishing those weapons, the promise was made that the United States would guarantee its sovereignty and security.  So when a conflict did arise with the nuclear armed Russian neighbor, they had no recourse but to hope for relief and protection from the United States.  But after Russia annexed the Crimea, we did nothing.  So to with the Supreme Court; when an act of egregious violation of sovereignty occurs, the USC mandates that the only recourse and redress is through the Supreme Court.  When they reject a hearing on that dispute they have violated the promise made.  This is also not unlike the philosophy of Gun Control on a smaller scale:  if you turn in your weapons, the State will be your protection; until it isn't, and you find yourself at the mercy of corrupt and evil men.

That is the general reasoning that this case should have been heard.  But what of this specific case?  Is there really a "dispute" here between States, or is it just a disagreement about how one State chooses to resolve its own internal affairs?  There is in fact one, and only one, caveat to the manner in which States conduct their affairs, guaranteed and therefore mandated by the USC.  Article IV Section 4 states that "The United States shall guarantee to every state in this Union a republican form of government..."  Most States in this Union would not join together to be governed by a President if any or most of those States were governed by a Monarchy, or by a Socialist Dictatorship, or a Despotic Junta.

When a State begins acting by Executive Fiat, it is no longer a "republican form of government".  When it no longer requires legislative authority, it is no longer a republic.  When it stops following its own Constitution, it is most definitely no longer a republic.  The Constitution envisions that the State's government would be besieged from within by anti-republican forces, and would require rescue from without.  But it is equally the case that the State government itself becomes corrupt, and will not seek Federal relief for its own violations of that guaranteed form.

Therefore, in that the other States of the Union will not be joined in government with a despotic oligarchy that denies a republican form of government to its people, they have the absolute standing to call into question the results of any vote taken by those several states.

We all agreed to lay down our arms, to not fight the petty border skirmishes of Medieval European fiefdoms, and to let peaceful adjudications occur through a Supreme Court.  We all agreed to form republican style governments, governed by Constitutions that lent authority through the consent of the governed.  Both of these essential pillars have been attacked, and the injured victim is the general consent of the people of this nation and its several States to be governed in Union.