This case study reviews a comparative research project on the political impact of extreme-right parties on their domestic political systems. Since most extreme-right parties are distinctive for their cultural xenophobia or biological racism, this research evaluates the impact of these parties on immigration politics and policy. Research on ERPs’ political impact had remained overlooked in political science literature, mainly due to the lack of interaction between political scientists focused on the politics of international migration and scholars interested in extreme-right parties. To attain the proposed objectives, the project employed a case studies approach, drawing on a small-N research strategy based on the selection of a limited number of cases: the United Kingdom, France, and Italy. Extreme-right parties’ impact on immigration politics and policy was disaggregated according to three distinct dimensions: interparty competition, public attitudes toward immigration, and the development of immigration control. A mixed-methods strategy was deployed to evaluate the extreme-right party impact on these dimensions that involved the combined employment of qualitative and quantitative research methods. This case study reviews the challenges faced during the research process inherent to the development of the proposed research project, ranging from the formulation of the research question, the justification of case selection, the choice of the research methods, and the problems faced through its implementation.