Two of Latin America’s twentieth-century revolutions occurred in 1910 in Mexico and in 1952 in Bolivia. In both cases, the campesinos, or rural poor, formed an integral part of the revolutionary coalitions that seized power, and the two postrevolutionary regimes that emerged came to rely on the campesinos for vital political support. Why, despite their similarities, did the postrevolutionary regime in Mexico (Partido Revolucionario Institucional or PRI) manage to retain the loyalty of the campesinos for much longer than its Bolivian counterpart (the Movimiento Nacionalista Revolucionario or MNR)? While a substantial body of literature exists on both these regimes, few scholars have ever explored comparative questions like this one. This study examines internal government correspondence from both regimes and articles from Mexican and Bolivian newspapers to explore and compare the linkages that connected these two parties to their peasant populations. This thesis argues that the PRI proved more effective at co-opting its campesino population for three reasons: 1) Social and cultural factors made the Mexican campesinos more receptive to co-optation; 2) Secondly, the PRI's bureaucratic structures for land allocation and aid distribution proved adept at leveraging resources for support; 3) The PRI possessed crucial links absent in the MNR, including a corporatist peasants’ organization and a functioning agrarian bank. As a comparative historical analysis, this provides a new perspective on both the PRI and MNR. Moreover, it enables a broader exploration of themes like party-building and the influence of cultural and social dynamics on the process.