This chapter addresses the problem of constitutional populism in the context of constitutional imaginaries as power formations and polity's self-identifications and self-constitutions. It argues that different forms and ideologies of populism and their constitutional risks and excesses, rather than external destabilising threats, can be treated as an intrinsic part of constitutional democracy. They are driven by the imaginary of authenticity of collective identity and its direct political expression uncorrupted by representative institutions and technocratic elites. The chapter particularly focuses on the imaginary of the public sphere and its constitution of the specific distinction between public opinion – the doxa and expert knowledge – the episteme and its impact on the imaginary of authenticity in constitutional democratic politics. It follows by exploring the imaginary of authenticity and its constitution of explosive communities in the context of Europeanisation and globalisation. Finally, it analyses the EU's responses to the imaginaries of constitutional populism, especially European public spheres and demoi. It concludes by stating that transnational European constitutional imaginaries integrate elements of constitutional populism while preserving the European integration's initial critique of the imaginary of nations living authentically and exclusively in their states.