The explanation is assumed as an essential feature of political studies as a special genre of political discourse. Two explanatory models, which have been developed in institutional political studies, are discussed in the article. Rational choice institutionalism and sociological institutionalism differ fundamentally in the understanding of social reality and the nature of social institutions. Deductive-nomological model inherent in rational choice institutionalism meets the requirements of logical positivism to a greater extent. Studied phenomenon is explained by applying general laws to it, i.e. by showing what happens in accordance with these laws in certain conditions. At the same time, such an explanatory model reveals some limitations. Firstly, “universalist claims”, which are inherent in rational choice institutionalism, fall under suspicion. Another serious problem is the inability to explain the phenomenon of rationality as such. Finally, the phenomenon of rationality requires taking into account the social context, since the explanation based on rationality is not just a logical abstraction suitable for any empirical material. On the contrary, it is suitable for the specific social context in which people act rationally. Sociological institutionalism uses such explanatory models as categorial schemes that are muchmore flexible in comparison with deductive-nomological logic. They allow us to specify the concepts used, split them, if necessary, into several components as well as to enter new concepts that fix those phenomena of empirical reality that previously were not perceived as significant ones.