"Paragraph 2 of Senate Rule XXII, also known as the 'cloture rule,' was adopted in 1917. It established a procedure, amended several times over the intervening years, by which the Senate may limit debate and act on a pending measure or matter. Aside from unanimous consent agreements and statutory limits applying to certain types of legislation, cloture is the only mechanism by which the Senate can limit debate. In recent years, some Senators have expressed renewed concerns over the way in which extended debate is conducted in the Senate and the operation of the cloture rule. Proposals for changing the cloture process include the establishment of new precedents on amending the rules, changes in the threshold necessary to invoke cloture, reductions in the time costs associated with certain cloture-related actions, and new or additional restrictions on debate in certain circumstances. This report provides a brief history of the Senate cloture rule, explains its main features and the arguments made by supporters and opponents of these features, outlines a range of proposals to change its operation, and briefly explains the methods by which the Senate might change its rules or practices."
CRS Report for Congress, R41342
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html