The article presents an original Keynesian-institutional approach to studying the macroeconomic dynamics of a transitional economy (on the example of Russia). The article proposes theoretical provisions related to the inclusion of an assessment of the institutional factor in the distribution of national income, as well as an authorial approach to modeling the relationship between institutions and aggregate demand based on the construction of linear regression equations, including changes in consumption, investment and institutional environment. Currently, economists have a desire to revise the mainstream and increase the requirements for the explanatory ability of macroeconomic models. The views widespread in economic theory are increasingly criticized due to the predominance of econometric analysis over qualitative interpretations, the unrealistic hypotheses of the rationality of economic agents’ behavior and the perfection of market mechanisms based on the assumption that it is possible to predict the future based on an analysis of the past. In order to solve the indicated problems, it is often proposed to use synthetic theories that combine the achievements of several schools of economic thought. One of these synthetic theories is Keynesian-institutional synthesis. The proposed approach is applied to assess the macroeconomic dynamics of the Russian economy, in which a decrease in consumption and investment volatility have been observed over the past five years, which is associated with macroeconomic stabilization and the development of social support institutions. However, the expectations of economic agents are rather unfavorable, and further measures are needed to stabilize aggregate demand. According to the analysis of official statistics, institutional factors significantly affect aggregate demand, but are not of priority. At the same time, the general conditions of the institutional environment have a stronger effect on investment than on consumption. On this basis, it has been concluded that the progress of institutions can not only accelerate economic growth, but also increase macroeconomic risks; therefore, it increases the responsibility of politicians for decisions in the field of economic regulation.