Política offers a stunning revisionist understanding of the early political incorporation of Mexican-origin peoples into the U.S. body politic in the nineteenth century. Historical sociologist Phillip B. Gonzales reexamines the fundamental issue in New Mexico’s history, namely, the dramatic shift in national identities initiated by Nuevomexicanos when their province became ruled by the United States. Gonzales provides an insightful, rigorous, and controversial interpretation of how Nuevomexicano political competition was woven into the Democratic and Republican two-party system that emerged in the United States between the 1850s and 1912, when New Mexico became a state. Drawing on newly discovered archival and primary sources, he explores how Nuevomexicanos relied on a long tradition of political engagement and a preexisting republican disposition and practice to elaborate a dual-party political system mirroring the contours of U.S. national politics. Política is a tour de force of political history in the nineteenth-century U.S.–Mexico borderlands that reinterprets colonization, reconstructs Euro-American and Nuevomexicano relations, and recasts the prevailing historical narrative of territorial expansion and incorporation in North American imperial history. Gonzales provides critical insights into several discrete historical processes, such as U.S. racialization and citizenship, integration and marginalization, accommodation and resistance, internal colonialism, and the long struggle for political inclusion in the borderlands, shedding light on debates taking place today over Latinos and U.S. citizenship.