This model, further, is usually contrasted to the parliamentary model, such as is found in Britain. It is argued that party plays a much more important role there because is party discipline in the House of Commons, there is centralized party leadership which determines the party’s position on policy questions, there is no dispersion of power as in the American constitutional system (Parliament is supreme), and external pressures play no such negative role (indeed constituency influences facilitate the relevance of party in the policy process). The majority in the party caucus (Labour, Conservative, or Liberal) in the House of Commons selects its leadership, together they decide on policy, defections from these majority decisions are not sanctioned but punished, and thus normally the party as an organization makes policy. There is, thus, theoretically a sharp contrast between the United States “fragmentation of party power” model and the parliamentary (British) “party dominance” model.