"'Populism' as a term was rarely used in the 20th century; it was limited to US historians describing, in highly specific terms, the original agrarian populists of the mid-19th century. Latin American social scientists (often Marxists) focused it primarily on the Peronists in Argentina. I only started to really engage with the term in the mid-1990s, while researching my dissertation on what was then still predominantly called 'rightwing extremism'. The German political scientist Hans-Georg Betz had just published what is still the best book on the topic, Radical Right-Wing Populism in Western Europe, and I dived into Leiden University’s library to find anything I could find on this odd term. The great British political theorist Margaret Canovan had written an excellent overview, simply titled Populism, in 1981, but argued that, while there were seven different subtypes, populism itself could not be defined. So I delved deeper, trying to engage with the work of the late Ernesto Laclau, an Argentinian post-Marxist theorist, undoubtedly the most influential scholar of populism for academics and politicians alike. ..."
Guardian
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