Scholars have long studied how social movements frame and deliver their messages, yet much less is known about how these “signals” are received by the public. In this study, we ask whether and how social movement members’ characteristics interact with a bystander’s to influence whether they support a particular protest movement. In addition, we examine how perceived likelihood of violence mediates these outcomes. We test five competing models based on previous theories of emotion, race, and political views in social movement support. To adjudicate between these frameworks, we conduct an experiment using a 2x2 factorial design in which participants read a news story about a protest accompanied by an image of a neutral/angry, white/Black protestor, measuring three types of social movement support. Results provide support for the politicized race model: a Black protestor is more motivating for liberals’ social movement support, while a white protestor is more motivating for conservatives. Both liberals and conservatives are more likely to associate the protest with violence after seeing a Black protestor compared to a white one. Racialized perceptions of violence explain part of conservatives’ hesitancy to support the movement when seeing a Black protestor and inhibits part of the otherwise-positive effect of seeing a Black protestor for liberals.