The opinion in which all justices agreed reads, "[The] congressional rule adopted under the Elections Clause (and its counterpart for the Executive Branch, Art. II, § 1, cl. 3) sets the date of the biennial election for federal offices, as  “[t]he Tuesday next after the 1st Monday in November… This provision, along with 2 U. S. C. § 1 (setting the same rule for electing Senators under the Seventeenth Amendment) and 3 U. S. C. § 1 (doing the same for selecting Presidential electors), mandates holding all elections for Congress and the Presidency on a single day throughout the Union.”