The process to ratify a constitutional amendment is complicated and time-consuming. The Archivist of the United States, who heads the National Archives and Records Administration, oversees the procedure. Congress can propose an amendment by a two-thirds majority in both the House and Senate. Alternatively, two-thirds of the states can call for a constitutional convention, though no amendment has ever been proposed in that manner. Once an amendment passes Congress, it must be approved by three-fourths of the states.