Testing the Populist Zeigeist. A cross-country analysis of populism across parties using supervised machine learning

Although scholars stressed populism's contagious, few studies empirically and comparatively explored the 'Populist Zeitgeist', that is the entrance of populist content into non-populist actors' political debate. We tested this hypothesis for Austrian, French, German, Italian, Spanish, and Dutch parties. For investigating populism's temporal and spatial variations in non-populists' political discourse, we used an automated score derived with textual analysis on national electoral manifestos from the early 2000s for nearly two decades. We found an increase in the average level of populism when pooling countries and looking at non-populists in aggregate; however, trends vary across nations and parties. Mainstream populism is substantial when looking at Italy, France, and Spain together, precisely across parties leaning towards right and centre. Nevertheless, Italian parties drive this increase. Consequently, we looked closely at the Italian case, finding evidence of a strong Populist Zeitgeist in national manifestos. We repeated the analysis using Italian leaders' speeches, obtaining comparable results. We concluded that, whereas there is no evidence of the Populist Zeitgeist in most countries we analysed, this phenomenon appears crucial in the Italian context, with causes possibly lying in the national political history and background.