We study lobbying in favor and against the most widely used trade barrier – antidumping (AD) duties. We combine detailed information from lobbying reports filed under the Lobbying Disclosure Act with data on AD duties to construct a unique dataset, which allows us to identify all firms that lobbied on US AD petitions and expiry reviews during 2008-2020. We document lobbying efforts in favor of AD protection (by import-competing US firms) and against it (by US downstream firms and foreign firms targeted by the duties). We examine the impact of these lobbying efforts on policy outcomes. To address endogeneity concerns, we will use an instrumental variables strategy, exploiting exogenous changes in political connections with members of the key trade committees in Congress. Joint with P. Conconi, E. Navarra, and L. Trimarchi.