This chapter tests the argument about new parties’ adoption of mobilization strategies in a context where they have limited access to organizational allies. Whereas most of the organizational allies discussed in Chapters 3 and 4 are major (often nationally organized) peak associations, MORENA could only rely on smaller, locally focused organizations. As this chapter shows, despite the different organizational structures, the shared experience of moments of solidarity also shaped whether party–organization ties later became institutionalized in this case; as a result, MORENA could consistently rely on organizationally mediated appeals. However, I find that the difference in the degree or level of organizational aggregation – aggregated/peak versus local organization – had important implications for the resulting party structures.

This chapter expands on the micro-level evidence from Chapter 6 on how effective one-off organizational endorsements are at swaying vote preferences by exploring how repeated organizational expressions of support over multiple years (due to a mechanism that institutionalized a new party’s ties with its organizational allies) can help new parties secure support in subsequent elections. Analyzing a natural experiment from Mexico, in which MORENA uses lotteries to select candidates for national public office, it shows how the party took root and mobilized voters more successfully in localities where it was able to tap into organizational networks through candidates who are embedded in local organizations.

This chapter explores the resulting party identification in the three cases. Drawing on original and existing survey data, it shows that membership in organizations that regularly support a new party is strongly associated with whether a voter develops an attachment to the party. Further analysis of the poster experiments suggests that the frequency of attending organization meetings is associated with the robustness of the attachment. Additional analyses of the natural experiment reveal that repeated organizational expressions of support over multiple years help new parties gain new followers. It then compares and contrasts this organizationally mediated path to partisanship (organizational cultivation), which can account for the development of robust partisan attachments to the MAS and MORENA, with an alternative path to partisanship that can yield party identification even for parties without organically linked organizational allies. In the case of Alianza PAIS, which could not rely on organizational cultivation through organically linked organizations, partisan attachments have developed in direct response to voters’ evaluations of the party’s performance.

During the last thirty years, Mexico saw two successful left-of-center political parties, the Partido de la Revolución Democrática (Party of the Democratic Revolution, PRD) and Movimiento de Regeneración Nacional (National Regeneration Movement, MORENA). The PRD was launched in 1989 and grew throughout the 1990s, becoming the second or third largest political force in the country. In 1997, the party won Mexico City’s mayoral post, which it retained until 2018. MORENA was officially born in 2014, in the midst of an internal PRD crisis, and quickly achieved electoral success, winning the presidency in 2018. The PRD and MORENA satisfy the definition of political party presented in the introduction to this volume, that is, a political organization that establishes horizontal coordination mechanisms among its leaders and vertically aggregates social interests. Moreover, the analytical model proposed by Luna et al. provides useful guidelines for studying the evolution of parties of the Mexican Left. In particular, this chapter highlights the heuristic value of analyzing the impact of the interaction between horizontal coordination and vertical interest aggregation. The case of Mexico illustrates that taking into account how parties connect with their environment helps explain the stability (or instability) of the party.