According to the Constitution, the President Elect must take the Oath of Office on December 1, before a joint session of Congress; the Constitution also states that the presidential term begins on December 1. Members of Congress belonging to the parties in the Coalition had threatened to disrupt the ceremony, with actions similar to those that prevented Vicente Fox from delivering his State of the Union address on September 1. According to the Constitution, if the elected president does not take the Oath of Office on 1 December before a joint session, the presidency is declared vacant and an interim president must be named and new elections called.