Research on populism(s) has to cope with the new constellations of political agency, communication and intermediation that have been triggered by the recent fundamental change of the public sphere. Under the impact of various crises, accelerated globalization and new information technology, this structural change has brought about a comprehensive mediatization of politics and a further push toward “populist democracy” (as a structure). After a summary of the insights into the mechanisms of populism comparative studies have generated, and an overview of the varieties of populisms through the 20th century, the second part of the paper will explore the impacts of the new “Strukturwandel der Öffentlichkeit” for the quality of democracies in the 21st century. The paper argues that “populism” is not always an external (authoritarian) threat to liberal democracy, but can also be generated from within the liberal script, if and when the partial regimes of “embedded democracy” get out of balance and the “populist” elements overwhelm the procedural and institutional checks.