The National Voter Registration Act (the NVRA) applies to all federal elections and creates a federal voter registration form that States are required to treat as sufficient when it comes to federal elections. Arizona argues that Congress can apply this requirement to House and Senate elections, but not presidential elections. The State’s theory is that the Elections Clause, Art. I Sec. 4, gives Congress the power to regulate the “manner” of House and Senate elections. But the Electors Clause, in Art. II, gives only the States the power to regulate “the manner” of presidential elections. The State wants to require those who want to vote in presidential elections to provide proof of citizenship, which the State requires for State elections. The NVRA, as interpreted by the Supreme Court, would not permit the State to impose this requirement for federal elections, and Arizona now argues the NVRA is unconstitutional as applied to presidential elections.

This is a major issue, since it implicates the general question of Congress’ power to apply its general election regulatory requirements to the presidential election. The case is in an usual procedural posture, because the Republican Party of Arizona [corrected] is asking for a stay from the Court before the Court of Appeals has heard the case.

Derek Muller posted about these issues at an earlier stage of the litigation. See here