How do political parties emerge? Prevailing understandings conceive parties forming as reflections of pre-constituted social sectors, seizing divisions that exist in society prior or independently of the party itself. The advent of parties has also been understood as an after-effect of democratization undertaken by modernizing states. My dissertation tests these theories by asking why the Partido Revolucionario Institucional (PRI) in Mexico emerged as a mass party after the revolutionary upheaval of the early twentieth century, while Bolivia’s Movimiento Nacional Revolucionario (MNR) failed in undertaking a homologous process after the country’s revolution of the mid 1950s, despite attempts to do so and the presence of similar sectors available for mobilization and identical bureaucratic structures.

I develop a two-pronged argument contending that the emergence of parties requires the existence of a strong civil society upon which to act; in turn, the presence of this civil societal realm is facilitated by the collapse of ‘pre’-capitalist land tenure arrangements. The dissolution of village identity and traditional authority in Mexico and not in Bolivia – underpinned by the destruction of communal property – permits the emergence of a civil societal realm of unions and organizations. This realm enables the articulation of demands and interest aggregation in a way compatible with the party-form. Hence, I show the power of the party to shape and construct political constituencies; at the same time, by pointing to the role of property arrangements, I identify structural determinants to the capacity for political organizations to produce constituencies. To control for differences between countries, the dissertation is organized around four subnational case studies showing how both inter- and intra-country variation in party formation is explained by examining the relationship between land privatization and organizational absorption.