In June 2005 the Dutch electorate rejected the EU constitutional treaty in a national referendum. The current study, which focuses on vote choice and the campaign, draws on complementary explanations for referendum voting behavior. We investigated how attitudes towards the EU influenced the intention to vote No ahead of the campaign as well as the impact of the campaign and the media on the final vote. Therefore, we combined a media content analysis (n = 6,643) with panel survey data (n = 1,379). Results reveal that prior to the actual start of the campaign, existing skepticism towards the EU was the strongest determinant for the intention to vote No and served as a mediator for the influence of other relevant factors such as disapproval of the incumbent government, feelings of national identity and fear of globalization. During the campaign the referendum topic was highly visible in the news with a positive tone towards the Constitution. In this context, higher levels of exposure to referendum news increased the likelihood of voters to switch over to the Yes side.