The provision of external state support to non-state armed groups in civil wars is a dynamic process. The calculus of state sponsors varies over time, which means that assistance provided to the armed opposition fluctuates. While we know much about the initiation of external support and its effects, we know less about why state sponsorship changes over time. To address this, I propose a theoretical argument that can account for policy adjustments over time. The theory builds on the notion that leaders change their support commitment when there is adverse feedback and that support increases as long as the causes of policy failure can be attributed to external actors, while cutbacks occur when failure is attributed to the state sponsor’s own actions. Process-tracing is used to illustrate the value of this framework in a within-case analysis of the United States’ support commitment to the armed opposition in Nicaragua in the 1980s. The study demonstrates the utility of focusing on shifts in leaders’ perceptions and domestic attribution processes rather than structural features of the international system or rebel behavior to understand temporal variation in external support.