Election campaigns are more than simple competitions for votes; they also represent an opportunity for voters to become politically knowledgeable and engaged. Using a large-scale web panel (n≈5,000), we track the development of political knowledge, internal efficacy and external efficacy among voters during the 2011 Danish parliamentary election campaign. Over the course of the campaign, the electorate’s political knowledge increases, and these gains are found across genders, generations and educational groups, narrowing the knowledge gap within the electorate. Furthermore, internal and the external efficacy increase over the course of the campaign, with gains found across different demographic groups, particularly narrowing the gaps in internal efficacy. The news media play a crucial role, as increased knowledge and efficacy are partly driven by media use, although tabloids actually decrease external efficacy. The findings suggest that positive campaign effects are universal across various media and party systems.