His current position is as Professor of General and Comparative Political Science at the Department of Political Science, University of Copenhagen, where he has held various positions since 1991, and where he specializes in political institutions, political economy and American politics, especially issues such as elections, voting systems and constitutions. Before his current appointment, he was professor (2005–06) and associate professor (2000–05) at the Dept. of Political Science and Public Management, University of Southern Denmark and assistant professor at the Dept. of Political Science, University of Aarhus (1998–2000). He has held visiting appointments at several institutions, including Saint Edmund's College at University of Cambridge, Nuffield College at Oxford University, the Institute for Social and Economic Research and Policy at Columbia University, the Dept. of Economics, New York University, and the Institute for Humane Studies, George Mason University.