Studies on ethnic interest groups are contributing to better understand the US foreign policy. By reviewing this literature, we noticed that establishing causal claims in this field has proved challenging due to methodological issues. Many authors draw conclusions focusing exclusively on ethnic groups without taking into account the full complexity of political processes. This work consists in the application of the advocacy coalition framework (ACF) to this subject, aiming to overcome previous limitations by analyzing the links between ethnic groups and other agents. To that end, we undertook the case study here reported of the role played by Indian–Americans to advance the 2008 nuclear agreement between the United States and India through Capitol Hill. Employing deductive process tracing based on the ACF's structure, we demonstrate the relevance of the links between Indian–Americans and other groups to better understand how this agreement came to be approved.