This article examines the tensions between the Gran Colombian republican constitution of 1821 and Simón Bolívar's fear of a mulatto takeover. It focuses on Cartagena in the 1820s, where the mulatto general José Padilla challenged the socio-racial hierarchy and accepted notions of equality of the city, heading a three-day coup in 1828 against Bolívar's attempt to impose a new authoritarian constitution. Padilla failed to rally the mostly African-derived population of Cartagena behind the republican views of Francisco de Paula Santander and was promptly executed. Using the protagonists' correspondence, manifestos, criminal investigations, consular reports and censuses, the article analyses the factors in the city's demography, political leadership and culture, and in the composition of its military forces, that explain Padilla's failure. It highlights the role played by race and by Bolívar's views of mulattos in the process.