During the twentieth century, the United States shifted from embracing protectionism to being an advocate for global free trade. Scholarly debate has focused on whether this shift was solely because of changes in preferences or if changes to institutions also played a role. Relying upon access point theory, this article argues that an institutional change, delegation to the President, led to endogenous changes in preferences. Delegation makes it harder for interest groups to gain access to policy makers, which should raise the costs of all lobbying. As protectionists dominate lobbying due to their collective action advantage, they will be disproportionately hurt. Thus, delegation should lead to less lobbying and lower tariff rates. These arguments are tested on time series data of tariff rates using an Error Correction Mechanism model and on data on interest group testimony before Congressional committees.