Scholarly studies of U.S. legislators’ voting behavior have concluded that constituent interests exercise only limited influence, but these conclusions may result from inadequate measurement. I develop new measures of economic interests that emphasize import/export (sectoral) cleavages in addition to business/labor (factoral) cleavages and, in the process, transcend geographic boundaries. Results of logistic regression analysis suggest that the interests of economic and nongeographic constituencies, as reflected in campaign contributions, were highly significant predictors of voting in the U.S. Congress on the U.S.–Korea Free Trade Agreement and that the import/export cleavage was more salient than the business/labor cleavage. In addition, legislators’ ideological positions with respect to national security were more significant than their partisan affiliations and more significant than their positions on other dimensions of ideology.