From a socio-theoretical and media-theoretical perspective, this article analyses exemplary practices and structural characteristics of contemporary digital political campaigning to illustrate a transformation of the public sphere through the platform economy. The article first examines Cambridge Analytica and reconstructs its operational procedure, which, far from involving exceptionally new digital campaign practices, turns out to be quite standard. It then evaluates the role of Facebook as an enabling ‘affective infrastructure’, technologically orchestrating processes of political opinion-formation. Of special concern are various tactics (...) of ‘feedback propaganda’ and algorithmic-based user engagement that reflect, at a more theoretical level, the merging of surveillance-capitalist commercialization with a cybernetic logic of communication. The article proposes that this techno-economic dynamic reflects a continuation of the structural transformation of the public sphere. What Jürgen Habermas had analysed in terms of an economic fabrication of the public sphere in the 1960s is now advancing in a more radical form, and on a more programmatic basis, through the algorithmic architecture of social media. As the authors argue, this process will eventually lead to a new form of ‘infrastructural power’. (shrink)