Mark Elchardus and Bram Spruyt* Populism, Persistent Republicanism and Declinism: An Empirical Analysis of Populism as a Thin Ideology Populism is usually studied by looking at the electoral and rhetorical strategies of parties considered to be populist. In contrast, this article attempts to measure the support for the core propositions of populism among voters and explain the social differences in that support. On the basis of a survey of the Dutch-speaking population of Belgium (N: 2,330) we find that this support for populism turns out not to be directly influenced by a weak or uncertain economic position, by dissatisfaction with personal life or feelings of anomie. Support for populism appears foremost as a consequence of a very negative view of the evolution of society – declinism – and of the feeling of belonging to a group of people that is unfairly treated by society. RESEARCH CONCERNING POPULISM HAS, ALMOST EXCLUSIVELY, focused on the so-called ‘supply side’ of politics: populist ideology (for example, Stanley 2008), populist rhetoric (for example, Rooduijn and Pauwels 2011) and the societal developments explaining the rise of presumably populist parties (for example, Boomgaarden and Vliegenthart 2007). This article follows a different track. It investi- gates the extent of the acceptance of (core elements) of populism among the electorate. Very little is known about the distribution of populist attitudes in the population. We will argue that the spread of populist attitudes cannot be deduced from the success of (pre- sumably) populist parties, but can only be mapped on the basis of a measurement of populist attitudes. There have been previous attempts at scale-development in order to measure populist attitudes (for example, Akkerman et al. 2014; Hawkins et al. 2012). This article * Mark Elchardus is Professor of Sociology at the Free University of Brussels. Contact email: mark.elchardus@vub.ac.be. Bram Spruyt is Assistant Professor of Sociology at the Free University of Brussels. Contact email: bram.spruyt@vub.ac.be. Government and Opposition, Vol. 51, No. 1, pp. 111–133, 2016 doi:10.1017/gov.2014.27 First published online 30 September 2014 © The Authors 2014. Published by Government and Opposition Limited and Cambridge University Press https://doi.org/10.1017/gov.2014.27 Published online by Cambridge University Press