My research focuses on political parties in all their facets. I examine parties at the local, national, and European levels.

Local Politics

Local representative democracy is based on the assumption that voters through their vote for a party have control over policy choices in their municipalities. There is remarkably little research on local party politics in the Netherlands but also comparatively. Therefore, I am investigating the role of parties at the local level.
This figure, based on the Netherlands Local Manifesto Project, shows the position of branches of Dutch political parties and independent local parties on the left-right dimension in 2018.
  • To gain an understanding of where local parties and branches of national parties stand in the political landscape, I initiated the Netherlands Local Manifesto Project. This is a collection of election programs from municipal council elections since 2014. It is now the largest collection of election programs in the world.
  • Together with doctoral candidate Thijs Vos and postdoctoral researcher Marijn Nagtzaam, I am researching the behavior of parties in municipal councils. With financial support from the Ministry of the Interior and Kingdom Relations, the Thorbecke Chair, and the Netherlands Organisation for Scientific Research, we gather information on the use of council instruments by council factions and voting behavior in municipal councils.
  • I am also conducting research on local voting behavior. In 2023, along with colleagues from Utrecht University and the University of Twente, I held the Provincial and Water Board Voter Study.
  • I am also involved in researching local political elites. In 2020, together with Anne Rasmussen from the University of Copenhagen, I conducted a survey among local politicians focusing on how they deal with public opinion. In 2024, along with colleagues from Utrecht University, the University of Twente, and Tilburg University, I held the Basic Monitor Political Office Holders. In this, my own research focuses on how local factions distribute work.

National Level

This figure based, on the Dutch Parliamentary Behaviour Data base, shows the position of party groups in the Dutch parliament between 2022 and 2023.

Parties form a central link in national politics. I am involved in numerous projects focusing on parties at the national level. My research has a European scope, with a particular emphasis on the Netherlands.

  • Parties play a significant role in structuring the work of the Dutch Parliament. Together with Tom Louwerse and Cynthia van Vonno (both from Leiden University), I have established the Dutch Parliamentary Behaviour Database. This database collects information on parliamentary behavior (voting behavior, use of instruments, and speeches) in the Dutch Parliament since 1918. This data has been utilized in numerous publications about the Dutch parliament.
  • Parties also play a crucial role in election campaigns. I coordinate the data collection for the Comparative Manifesto Project for the Netherlands. This project focuses on the themes emphasized by parties in their programs. We have coded election programs from parties represented in the Dutch Parliament since 1982 using in a Comparative Agenda Project scheme. This data has been employed in numerous publications about parties.
  • New parties often emerge along new ideological fault lines. My own doctoral research addressed how new parties are able to translate these fault lines into politics. Since then, I conducted research on nearly new parties entering in the Dutch Parliament to understand who votes for them.
  • In a representative democracy, the relationship between political parties and interest groups is of great importance. I study this relationship as a Dutch researcher for the PAIRDEM project. I have also contributed to the Left-wing Parties and Trade Unions project and INTEREURO, a project aimed at mapping the European interest group population.

European level

This figure shows the voting patterns in the eight European parliament.

Political parties play a crucial role in European politics. In Europe, I focus on two themes: voting behavior in the European Parliament and the relationships between national and European parties.

  • Together with Harmen van der Veer (Leiden University) and other colleagues, I conduct research on voting behavior in the European Parliament. Our central question is whether other divides beyond the traditional left-right and pro- versus anti-European integration positions are visible on specific issues.
  • With Gerrit Voerman (University of Groningen), I am researching the development of European political parties (“political parties at the European level”), focusing particularly on the European Green Party and the Alliance of Liberals and Democrats for Europe, and the role that national parties play in this form of party-political European integration.


My methodological specialization is scaling and data reduction methods, such as quantitative textual analysis and analyses of parliamentary voting. Additionally, I have experience with both quantitative and qualitative research methods (including interviews, archival research).