Political organizations and clubs structure contemporary politics. From political parties to environmental organizations, citizens join a host of associations to influence policymaking and the political agenda. Yet why do citizens in some western democracies join political organizations much more than in others? Laura Morales explains that there are three types of participatory patterns: a North American model, with extensive membership levels and a reasonably high level of activism within organizations; a northern, or Protestant, European pattern, that combines extensive membership levels and fundamentally passive involvement; and a south European model, where low levels of membership are compensated by intense activism. Drawing on a large number of crossnational surveys and datasets, Morales shows that huge crossnational variations in political membership are not so much related to social or attitudinal differences between these countries' citizens but are explained to a great extent by the structure of the political system of each nation.