Disability is a human universal and a complex social category with far-reaching implications for American law and public policy (Bagenstos, 2000; Scheer and Groce, 1988). Yet, little is known about the potential implications of disability for political psychology. Drawing on research in public opinion, social and political psychology, public policy, and disability studies, this dissertation presents a new theoretical framework and empirical evidence for disability as a dimension of political identity and cohesion in the American mass public. Conventional wisdom suggests that the development of strong political identities among members of diverse social categories emerges primarily as a consequence of (1) elite mobilization, and/or (2) intragroup contact and acculturation. In Chapter 2, I argue that while conventional wisdom is largely inapplicable to disabled Americans, disability may become politicized via two alternate social processes: individualized experiences of disability-related stigma and discrimination, and exposure to public policies targeted at disabled Americans. I find empirical support for this theory using data from four original national surveys of American adults with disabilities. In Chapter 3, I derive a new empirical measure for identification with disability - the Disability ID scale - using survey items common to existing work in political identity. I show that Disability ID varies in strength based on the prominence of disability in individuals’ everyday social experience, and is strongly associated with feelings of pride and group consciousness. In Chapter 4, I demonstrate the far-reaching implications of Disability ID for political attitudes. Disability ID is associated with ideological liberalism, Democratic partisanship, and support for a wide array of redistributive policies that stand to benefit disabled Americans. I build on these findings further in Chapter 5 by showing that Disability ID moderates responses to disruptive protest action undertaken by in-group members. In a pair of survey experiments, I find that respondents high in Disability ID are more tolerant of disruptive tactics and more willing to participate in costly forms of collective action. I also find suggestive evidence that strongly identified PWD are more attentive to the behavior of in-group members and may be more likely to disapprove of risky or obnoxious political action that risks the reputation of the in-group. In Chapter 6, I discuss the implications of these findings for our understanding of disability in politics, and more broadly for research in public opinion and political psychology. I argue that while disability is widely stereotyped as a source of personal limitation and stigma (Nario-Redmond, 2019), this dissertation suggests that for many Americans, disability is an important source of political identification and empowerment.