While the politicization of ethnic identities is readily observed around the world, a generalized understanding of what makes members of a particular group more likely to coordinate their votes towards a single party or candidate remains elusive. This Element scrutinizes voting patterns at the social group level based on individual-level survey data and controlling for country-level variables across 115 countries. The findings highlight how the characteristics of ethnic groups, especially size and crosscutting patterns, interact within political institutions. Three group-level characteristics are especially influential to bloc voting – stronger geographic concentration, greater internal alignment of group members across other identity dimensions, and groups whose members are more distinctive across identity dimensions compared to the broader population. When analyzed across political institutions, the highest rates of bloc voting occur among small groups with low crosscutting in permissive settings and medium groups with low crosscutting in restrictive settings.