"Because of the fear of possible terrorist attacks which could be directed at election facilities or voters in the States just prior to or during the elections in a presidential election year, attention has been directed at the possibility/authority to postpone, cancel or reschedule an election for federal office. The United States Constitution does not provide in express language any current authority for a federal official or institution to 'postpone' an election for federal office. While the Constitution does expressly devolve upon the States the primary authority to administer within their respective jurisdictions elections for federal office, there remains within the Constitution a residual and superceding authority in the Congress over most aspects of congressional elections (Article I, Section 5, clause 1), and an express authority in Congress over at least the timing of the selections of presidential electors in the States (Article II, Section 1, clause 4). Under this authority Congress has legislated a uniform date for presidential electors to be chosen in the States, and a uniform date for congressional elections across the country, which are to be on the Tuesday immediately following the first Monday in November in the particular, applicable even-numbered election years. This report will be updated as events warrant."
CRS Report for Congress, RL32623