The central aim of this chapter is to develop what we mean by Political Knowledge Regimes. We will first introduce the contemporary debate on expertise and democracy. We begin by presenting the main features of the technocratic tradition—from Plato’s Philosopher-King to the present day—and the different definitions of the voice technocracy in contemporary social sciences. Following Daniele Caramani, we analyze the tension between technocracy and democracy. Thanks to Zeynep Pamuk, we discuss in what concrete ways science should be used in modern democracies so that the authority of citizens is not eclipsed by the voice of experts. We argue, with her, that for the authority of science not to encroach on that of the citizenry, it is crucial to admit dissent among scientists (instead of repressing it) and to design institutions that allow the citizenry to decide in which specific scientific findings they prefer to place their trust. Then, we will present the definition of Knowledge Regimes proposed by John Campbell and Ove Pedersen. We justify the need to give this definition a “political twist” in order to incorporate the main features of the demand-side of the relationship between knowledge and policies. To be sure, the concept promoted by Campbell and Pedersen is a major contribution to the literature on the bridge between research and public policy. It helps us to understand the supply-side, i.e., the concrete form assumed, in each country, by the organizational machinery that produces information and ideas for public policy. We argue that, despite its merits, this concept does not shed light on national differences in how knowledge is used in public policy. In other words, we argue that in addition to the supply of professional expertise we need to understand the demand for that expertise. To account for these differences, it is necessary to know what factors affect the demand for knowledge from political elites. To this end, we elaborate the concept of Political Knowledge Regimes. We propose that the concrete form assumed by the demand for social research in each country depends fundamentally on two ideational dimensions. We name the first of these as the delegative dimension. It refers to the extent to which the elite in each country is willing to delegate crucial decisions to experts. We name the second as the partisan dimension. This one refers to the problem of how the political elite interprets the link between knowledge and political parties.