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.