In this dissertation, I analyze the protest politics of El Comite-MINP, one of the main organizations of the Puerto Rican Left in New York City in the 1970s. My study examines the impact of national identity, racial discrimination, and class, as well as political and ideological development, on the activism of Puerto Ricans who joined a contentious housing movement on Manhattan's West Side and gradually transformed from a community action collective to a Marxist-Leninist cadre organization.;Based on the analyses of various contentious campaigns -- including the squatters' movement against urban renewal (known as Operation Move-In), struggles for bilingual education and media inclusion of Latinos, protests by minority construction workers' against job exclusion, student strikes for access to quality higher education, and community-based opposition to the closing of Metropolitan Hospital -- this study demonstrates the partial effectiveness of protests that used disruptive tactics and persuasive, inclusive mobilizing frames, to elicit concessions from elites. Local and national structural changes, combined with internal ideological tendencies, reduced opportunities for successful protest outcomes in the second half, as compared to the first half of the decade.