The 2015 study consists of three main complementary components: The Post-election survey, the Panel / Rolling Cross-Section survey, and the Candidate survey. The main difference compared to previous studies relates to the mode of data collection; the main emphasis was now moved towards web interviews. The other main innovation was the addition of a four-wave panel survey. As in 2011, novel thematic modules of particular salience to researchers were included in the different surveys, while keeping the necessary continuity in the core questionnaire of the Post-election survey for comparison with previous waves. Post-election survey: The post-election survey consists of 5,337 web and telephone interviews. The survey was done in a sequential mixed mode with web offered as the first option: 82% responded in this way, while 18% responded by telephone. The sampling was based on a representative sample of 2’600 Swiss citizens with an oversampling of small cantons to have at least 80 interviews per canton. An additional oversampling was done in the cantons of Zurich, Geneva, and Ticino. Panel / Rolling cross-section (RCS): New for the 2015 study is a panel survey that studies the evolution of opinion and vote intention/choice during the different phases of the election cycle. Four waves were conducted: the first before the main campaign period, the second during the campaign, the third after the elections, and the fourth after the election of the Federal Council. 11’073 individuals responded to the first wave and 6’552 responded to the first three waves. The second wave was conducted as a Rolling cross-section, where around 120 individuals were interviewed daily during 61 days. A media analysis was also conducted in the context of this survey. Candidate survey: The candidate survey was carried out among all candidates for the National Council and the Council of States in the framework of the Comparative Candidate Survey (CCS) project, based on the Round II questionnaire. The survey collects data on the biography, campaign activities, and policy position of the candidates. Among others, the information gathered makes possible the study of underlying factors of candidates’ electoral success, as well as of issues of representation and linkage between voters and elites.