Prior literature establishes a positive relationship between democratic institutions and state informational capacities, yet the mechanisms driving this relationship remain debated. This paper contributes to this debate by examining how electoral competition at the subnational level created the incentives for democratic challengers to increase civil registration of unfranchised voting-age adults. We focus on the case of Mexico during the regime transition years (1990-2000) when several electoral reforms enabled electoral competition and increased voting transparency in local and federal elections. We argue that democratic challengers sought to secure electoral advantages in districts they controlled by informally relaxing enforcement of bureaucratic requirements to register unfranchised voting-age adults (forbearance), thereby expanding their voter base. We show empirical evidence for our argument using a difference-in-difference design, we find that municipalities won by the opposition parties were more likely to register voting age adults at a higher rate in years following the election, compared to municipalities won by the ruling PRI (Partido Revolucionario Institucional). Additionally, municipalities governed by opposition parties showed increases in voter registration and electoral participation in subsequent elections. Our findings suggest that similar mechanisms may apply in other countries where political participation was limited prior to democratization. Our paper highlights the critical connection between legal identity and political rights, as a birth certificate is a prerequisite for obtaining Mexico’s national voter ID card (“Credencial de Elector-INE”). Our study demonstrates that democratization can enhance state legibility by incorporating previously disenfranchised populations, particularly poor, rural, ethnic voters into the political process.