This dissertation explains how variations in white identification matter for white engagement with racially inclusive political projects in the United States. I argue that there are two dimensions of white identity. The first is called consciousness and indicates the extent to which individuals identify with the white racial group. The second is called valence and indicates how individuals interpret this white racial group membership. When individuals have negative valence, they interpret their whiteness as something that disadvantages them. Conversely, when an individual has positive valence, they see the benefits and advantages that they gain as a member of the white racial group. Valence is important for what kinds of racial narratives they use to understand complex political issues. The dimensions of consciousness and valence are continuous and intersecting: individuals can identify with their whiteness in a multitude of ways, but where they fall on these two dimensions is important for both their level of political efficacy and engagement, and what kinds of political issues they support. In this dissertation I draw on two primary sources of data. First, a series of in-depth interviews of white residents of the Twin Cities in Minnesota that took place during the spring and summer of 2020. Second, a series of original surveys on a national sample of non-Hispanic white Americans in 2022 and 2023. Crucially, this dissertation introduces new methods of measuring white consciousness that correct for problems of existing measures, and a new measurement for valence. I evaluate the validity of these new measures and find that they are related but distinct dimensions of white racial attitudes. I then analyze the implications of consciousness and valence for white political attitudes and behaviors. I find that individuals with higher white consciousness have a greater sense of political efficacy have a higher likelihood of participating in politics, especially in costly or extra-institutional ways like volunteering for a political organization or attending a protest. This is particularly the case if they also have positive valence. I also find that valence is important for what kinds of political issues white identifiers support. Individuals with positive valence are more supportive of the politics of racial inclusion, and those who have high consciousness and positive valence can even be mobilized to become actively involved in political movements for racial inclusion like Black Lives Matter. The contributions this dissertation makes are thus threefold. First, it provides a new theory of white identity that varies along the dimensions of consciousness and valence and can thus be informative for understanding differences in white political behavior. Second, it addresses issues of conceptualization and measurement in existing work using a sequential mixed-methods research design. These new measures are grounded in theory and drawn from the input of multiple rounds of qualitative and quantitative data collection. Finally, by showing how white identity varies along two dimensions, this research provides a direct link between how whites interpret their racial group membership and the variations in political and behavioral outcomes that are shaped by consciousness and valence.