Research on mass opinion in international political economy overwhelmingly relies on survey data. This poses problems of external validity, especially for a frequently low-salience issue such as trade policy. To examine whether survey findings about attitudes toward economic openness apply outside of surveys, this note considers patterns of voting in the 2007 Costa Rican plebiscite about joining the Central American Free Trade Area. Several extant theories appear to explain voting patterns, but the results are less in line with traditional economic models based on locally important economic sectors.