What distinguishes race, ethnicity, and nationhood as categories of political identity? How can we explore the commonalities and dissimilarities between these three categories of political identity? Most of the existing scholarship has looked at one or another of these forms of identity in isolation. I compare these three forms of identity by examining one case of peoplehood within the federal political system that we call the United States. Puerto Ricans are an ideal case study because they are a group that can exhibit racial, ethnic, or national political identities, depending on where they find themselves in the United States. Puerto Ricans on the island have a primary political identity that reflects their sense of nationhood. This is characteristic of sub-state national societies in multinational democracies. Puerto Ricans in the continental United States are racialized and ethnicized by the mainstream, majority culture. Their primary political identities become racial or ethnic, although this takes place through a process of contestation, negotiation, and relativization.