A study was conducted to determine the role played by media use diversity in shaping public opinion during the 1979 campaign to elect a representative from Great Britain to the European Parliament. The study focused on the British audience's evaluation of the clarity of the campaign issues as presented in the media and on individual cognitions about Europe formed prior to the campaign (cognitive stability). Data used in the study were gathered through interviews conducted with 372 potential voters in two separate cities. Subjects responded to questions concerning their perceived clarity of the campaign issues, their personal opinions concerning Europe, and the extent of their exposure to various media. Results indicated that people equally exposed to election information from different media during the campaign had a more confused perception of the campaign issues and showed higher levels of cognitive instability than did individuals who were exposed to only one source of information. The findings suggest that if exposure to the campaign had been measured only in terms of reliance on a single news source, it would show that media use reinforced previously held opinions. However, measuring communication exposure in terms of diversity revealed that the media were able to change opinions. (FL)