In most controversies in occupational and environmental health, to support a cause is primarily to establish causal links between facts and damage. From the study of the recent mobilization of the French nuclear test veterans and the controversy surrounding their health impact, this paper analyzes the processes that are central to this “politics of causation” and the forms it may take. It also shows that this politics of causation has a feedback effect on the definition of political cause and identity of the group. Capturing the dynamics of mobilization comes through studying the relationship between the often sensitive political issue and politics of causation.