Harald Schoen is Professor of Political Science, University of Mannheim. He is one of the principal investigators of the German Longitudinal Election Study (GLES) funded by the German Science Foundation. He has widely published on political behaviour, political psychology, public opinion, and political online communication. Sigrid Roßteutscher is Professor of Sociology in the Department of Social Sciences, Goethe University, Frankfurt am Main. Her research interests focus on politics and religion, social capital, political participation, electoral turnout, and social inequality. Her publications include Citizenship and Democracy in an Era of Crisis (co-edited with Thomas Poguntke, Rüdiger Schmitt-Beck, and Sonja Zmerli, Routledge, 2015). Rüdiger Schmitt-Beck is Professor of Political Science, University of Mannheim. His research focuses on electoral behaviour and political communication. His publications include Voters on the Move or on the Run? (co-edited with Bernhard Weßels, Hans Rattinger, and Sigrid Roßteutscher, Oxford University Press, 2014) Bernhard Weßels is a Senior Fellow at the WZB Berlin Social Science Centre and Professor of Political Science, Humboldt-University Berlin. He is one of the principal investigators of the German Longitudinal Election Study funded by the German Science Foundation, and was member of the Planning Committee of the Comparative Study of Electoral Systems (CSES) from 1998 to 2014. He has widely published on electoral behaviour, interest intermediation, and political representation nationally and internationally. His publications include Voters on the Move or on the Run? (co-edited with RüdigerSchmitt-Beck, Hans Rattinger, and Sigrid Roßteutscher, Oxford University Press, 2014). Christof Wolf is President of GESIS Leibniz-Institute for the Social Sciences and Professor for Sociology, University of Mannheim. His research interests currently focus on social stratification, research methods, and research infrastructures. His publications include The Handbook of Survey Methodology (co-edited with Dominique Joye, Tom W. Smith, and Yang-Chi Fu, Sage, 2016).