This chapter sets out the theoretical foundations for the growth model perspective, which is part of comparative political economy (CPE). Baccaro and Pontusson proposed a new analytical framework for CPE, called post-Fordist growth models (GMs), which is a demand-side approach and opens up a whole new research agenda. The two major innovations resulting from GMs are, first, moving on from the Varieties of Capitalism thesis, which has been the dominant paradigm in CPE for the past 25 years, and, second, combining institutional analysis within a demand approach, and in particular Kaleckian macroeconomics. The chapter discusses both theoretical frameworks. It presents the theoretical approach used in the book, referred to as the “social-structural” analysis. Fordist and post-Fordist stages give rise to different GMs, so that in the crisis of the Fordist period we find the germ of the characteristics of the post-Fordist period, which through a series of institutional and economic changes has given rise to a new stage.