Book excerpt: Although the relationship between digitalisation and democracy is subject of growing public attention, the nature of this relationship is rarely addressed in a systematic manner. The common understanding is that digital media are the driver of the political change we are facing today. This paper argues against such a causal approach und proposes a co-evolutionary perspective instead. Inspired by Benedict Anderson's "Imagined Communities" and recent research on mediatisation, it introduces the concept of mediated democracy. This concept reflects the simple idea that representative democracy requires technical mediation, and that the rise of modern democracy and of communication media are therefore closely intertwined. Hence, mediated democracy denotes a research perspective, not a type of democracy. It explores the changing interplay of democratic organisation and communication media as a contingent constellation, which could have evolved differently. Specific forms of communication media emerge in tandem with larger societal formations and mutually enable each other. Following this argument, the current constellation reflects a transformation of representative democracy and the spread of digital media. The latter is interpreted as a "training ground" for experimenting with new forms of democratic agency.