Scholarship in political science on race and its impact on political preferences has undergone substantial transformation in the last quarter century. Once defined racially by black and white, today the U.S. population is characterized by a multiplicity of racial and ethnic group divisions. Hispanics are now the largest minority population in the United States, followed by African Americans and then Asian Americans and Native Americans. The “multi-racial” population-a category formed by counting more than one racial group and allowed by the census since 2000-is among the fastest-growing groups.1 The United States is in the midst of the most significant wave of immigration in a century, and the vast majority of the newest Americans are no longer from Europe as they once were in the nineteenth century. Instead, more than half of today’s immigrants are from Latin America and another quarter come from Asia. While black migrants from Africa and the Caribbean constitute a much smaller share of new immigrants, their presence creates important diversity within the racial category of black.2 In this chapter we take the increased racial and ethnic diversity of the United States as a starting point, and analyze the significance of race and the group bases of political preferences. We begin with a discussion of categories of race and ethnicity in the United States and argue that these divisions are based not in “objective” biological difference, but rather in social constructions formed through the institutions and practices of U.S. government and society.3 Next we focus on individual-level measurements of psychological attachment to groups-group identity and consciousness-as critical intervening variables between racial group classification and the formation of political preferences. The contours of the relationships between racial group identity, racial group consciousness, and public opinion, particularly for Latinos and Asian Americans, are especially challenging for scholars because these populations and their politics are in flux. Finally, we proceed to analyze additional factors that may differentially influence the political opinions of individuals, depending in part on their racial group classifications and attachments, including party identification and mobilization, interpersonal contact and the racial and economic context, and perceptions of and experiences with discrimination.