This case presents the research design used by Candidate and Leader Selection, a standing group of the Italian Political Science Association, for investigating open primary elections held to select candidates and party leaders in Italy. The lack of a legal framework that rules primaries raised several research challenges for studying participation in primary elections and for clarifying the features and attitudes of primary voters. A brief introduction summarizes the main research questions concerning the study of primary elections, providing a theoretical framework and empirical definitions as well. The peculiarities of the Italian case study are then detailed, while the core of the piece is devoted to the research protocol description. In particular, this case presents the research strategies implemented for addressing the study of participation in open primary elections by means of exit polls. In particular, this case details the research procedures adopted for the sampling procedures and the coordination of the research teams at the regional level, the training of interviewers for face-to-face interviews, the drafting of the questionnaire, and the practical solution implemented for administering the survey at polling stations.