Attempts to produce an unambiguous definition of populism fail to account for the current uses of the term in the ordinary language of politics and the dominant media. This article proposes to question the presuppositions of these uses rather than trying to circumscribe a phenomenon whose appearance of unity merely reflects these presuppositions. The ‘family resemblances’ between protest movements and parties in the United States and Europe should not hide the differences between particular configurations in different countries. From this point of view, attempts to forge a positive concept of left-wing populism are as unsatisfactory as the prevailing depreciative use of the notion by liberal elites.