The project performs a critical review of the cartel party theory, and inquires as to whether the party groups in the Swedish Riksdag (Parliament) have become increasingly more similar between the late 1980s and the early 2010s. A research team with extensive experience in parliamentary and party research, and with different specializations, addresses different problems in six distinct studies. Four sub-studies scrutinize the cartel party theory by exploring if the party groups have become more homogeneous regarding political and social experience, gender disparities, professionalization, depoliticization, and adjustment to a media logic at the expense of ideology. The fifth component of the project examines two competing ideas: are cartels between parties increasing the similarity between the parliamentary party groups, or can cultures within the party groups withhold traditional differences? Lastly, the sixth component criticizes the cartel theory for its predominantly rational approach and highlights the changing normative conceptions of representation in the party groups: is party loyalty decreasing in favor of individualization within the party groups? The project collects various types of material and uses a variety of methods: archive data, secondary analysis of parliamentary inquiries, analyzes of parliamentary debates and qualitative (including retrospective) interviews.