Are electoral institutions – such as closed primaries – associated with reduced levels of participation by people of color? We theorize and find that primary electoral institutions that bar independent voters from participating in first-round elections mechanically reduce participation in primary elections; and also reduce turnout among registered independents in second-round general elections. Closed primaries have large demobilizing impacts on Asian American and Latinx voters, as these voters are registered as independents at higher rates than whites. We examine nationally representative and validated survey data from 2012 to 2018. Open and top-two primaries are associated with higher turnout from independent voters of color in both primary and general elections. Implications are that party registration status and formal institutions differentially demobilize voters of color and whites.