Political scientists in the United States have in recent years become concerned with analysis of the rights and responsibilities of political opposition. This interest was initially stimulated by the much-quoted, and much-maligned, report of the Committee on Political Parties of the American Political Science Association in 1950 entitled Toward a More Responsible Two-Party System. It has been supplemented by the volume edited by Robert Dahl, Political Oppositions in Western Democracies. Academic rationale for this interest is reflected in the paradox posed by Dahl, who, having cited ‘ the right of an organized opposition to appeal for votes against the government in elections and parliament’ as being one of ‘the three great milestones in the development of democratic institutions’, is then obliged to admit that in the United States ‘it is never easy to distinguish “opposition” from “government”’, and that ‘it is exceedingly difficult, if not impossible, to identify the opposition’. Opposition in the United States political system is nonstructural because of the multiple access points for influence, and opportunities for preventing or inhibiting governmental action are numerous. No single institution illustrates this fact better than Congress. In speaking of Congress, commentators do not talk about ‘the opposition’. They may refer to ‘the minority party’ (and ‘the majority party’), yet even these terms cannot be used at times when the Senate and House are not controlled by the same party. Moreover, internal organizational and procedural patterns in the contemporary Congress allow many opportunities for minority coalitions to check executive policies favoured by a majority coalition in Congress, and such coalitions are often bipartisan.