Why do some parties formed by social movements develop top-down structures while others stay more open and responsive to their social bases? The first rigorous comparative study of movement-based parties, this book shows not only how movements can form parties but also how movements contribute to parties' internal politics and shape organizational party models over the long term. Although the existing literature argues that movement-based parties will succumb to professionalization and specialization, Anria shows that this is not inevitable or preordained through an in-depth examination of the unusual and counterintuitive development of Bolivia's MAS. Anria then compares the evolution of the MAS with that of other parties formed by social movements, including Brazil's PT and Uruguay's FA. In a region where successful new parties of any type have been rare, these three parties are remarkable for their success. Yet, despite their similar origins, they differ sharply in their organizational models.

'Anria not only explains how social movements can give rise to political parties, but also offers a provocative challenge to the conventional wisdom that parties are necessarily oligarchic in their internal organization. Drawing from extensive field research on the Bolivian MAS and its movement bases, he shows how independent grass-roots actors can hold party leaders accountable to popular constituencies. This is path breaking work that forces scholars to reexamine time-worn assumptions about the relationships between parties and movements.'

Kenneth M. Roberts - Richard J. Schwartz Professor, Cornell University, New York

'Party-building is hard. In Latin America and elsewhere, most new parties fail. When Movements Become Parties offers a theoretically innovative and empirically rich account of one of Latin America’s rare party-building successes. It also deepens our understanding of an important, yet under-theorized, path to party-building, social movementism. Anria makes a compelling case that social movement origins not only facilitate successful party-building, but may also enable new parties to maintain an unusual degree of grassroots participation. Extraordinarily well-researched, When Movements Become Parties offers an unparalleled look at how the MAS functions - from the inside out. This book will go down as a landmark study of one of contemporary Latin America’s most important new parties. Yet its theoretical lessons extend well beyond Latin America.'

Steven Levitsky - author of How Democracies Die

'While the neoliberal critical juncture has deeply challenged existing party systems all over the world, the era of parties is certainly not over. To the contrary, social movements that have been extremely critical of representative democracy have been very effective in creating movement parties - endowed with alternative visions of a just society and participatory democracy. What is more, as this thick ‘anatomy’ of the Bolivian MAS critically shows, autonomous social mobilizations might be crucial in counteracting Michelsian oligarchic trends and keeping the innovative potential of these parties alive. An extremely interesting reading for all those interested in social movements and political parties, as well as in the perspective for the Left, within but also beyond Latin America.'

Donatella della Porta - Director of Centre of Social Movements Studies (Cosmos), Scuola Normale Superiore, Pisa

'This theoretically grounded and empirically rich study of Bolivia's MAS powerfully challenges the conventional wisdom that political parties will inevitably de-emphasize bottom up participation and concentrate power and decision-making at the top. Comparisons with the PT in Brazil and FA in Uruguay shed further light on why some movement-based parties become hierarchical party organizations while others do not. When Movements Become Parties is an important and superbly crafted study that will withstand the test of time.'

Wendy Hunter - University of Texas, Austin

'Based on a carefully crafted comparative within-case research design focused on Bolivia’s governing Movement toward Socialism (MAS) party, Anria argues that the organizational strength, density, and autonomous capacity for social mobilization by popular constituencies form the causal mechanism that prevents a party from falling victim to oligarchic temptations … [The book] highlights the benefits of bringing ‘society back in’ to party analysis by stressing that social movements may not only become parties but are also a critical factor in explaining parties’ organizational structures and operation.'

Source: Perspectives on Politics

'A wonderful and timely contribution to the literatures on political parties in general and to movement-based parties in particular.'

Source: Latin American Politics and Society

'Anria’s work makes a substantial theoretical and empirical contribution to the literature on movement-based parties and on the potential trade-offs between representation and participation of the masses in Latin America.'

Roberta Rice Source: Perspectives on Politics

'When Movements Become Parties is a wonderful and timely contribution to the literatures on political parties in general and to movement-based parties in particular. Because the book’s prose and analyses are highly accessible, it can be assigned in graduate and undergraduate courses on Latin American or comparative politics.'

Tulia G. Falleti Source: Latin American Politics and Society

'Through a creative research methodology and ample evidence from extensive field research, Anria’s book fills the gap in literature surrounding so-called personalist Latin American parties, and especially how their organisational structure evolves over time.'

Sally Sharif - London School of Economics Review of Books