Texas v. Pennsylvania

The State of Texas sued 4 states where Biden narrowly won but in which Texas suspected erroneous election results, seeking an order from the US Supreme Court decertifying their results. 45+ states and territories and hundreds of people filed dozens of briefs in this case, all within 3 days. The fundamental claim was that an unjust election in some states violates the rights of the rest of the states. The Supreme Court's 7-justice majority found no legal basis for states to claim that they had been harmed by the internal election conduct of other states, and so declined to hear the case. The 2 dissenting justices argued that the Supreme Court should have heard the case so as to deny the complaint on its (lack of) merits.

This case was widely heralded as the last major legal challenge to the 2020 election results, the signal that there were no legal avenues left to pursue.