This chapter is concerned with the question of how national mainstreams are maintained today, under advanced liberal democracies ostensibly promoting multiculturalism, diversity, and political plurality. For this, I seek to examine the ongoing construction of what we might call the “unmarked” or “natural” citizen of a nation, the unquestioned subject of rights and state recognition that defines the interior of the national–political community and, with that, the naturalization of exclusions suffered by those deemed outside it. I want to inquire into the making of “the natural” with respect to this ur-citizen figure, the history of its naturalization, and of the struggles of various populations to claim an affinity with it. The central question here is how, under ostensibly pluralized democratic systems, does the unmarked citizen preserve its unique place at the heart of the political community? How are others kept out? Problems of boundary maintenance have long complicated majoritarian politics in Latin America, owing largely to the rather unusual ways in which its national mainstreams are constituted. In contrast with many parts of the world, dominant narratives of nation-making throughout the continent commonly organize ideas of “natural” citizenship and national belonging not around the purportedly autochthonous inhabitants of its territory, but rather around the hybrid figure of the mestizo, ideally representing a mixture of indigenous and Spanish ancestry. Since independence, the promise of political emancipation and equality for (racially codified) subaltern populations has remained tied to their potential for assimilation into mestizo society. As a location premised on mixture and integration, the unmarked citizen is thus by definition an expansive category in Latin America, one promising considerable instability and permeability of the space it marks out for itself in the national polity.