Over the past decade, ‘mainstream’ political parties in liberal democracies have been challenged by rising support for insurgent populist movements that reject the status quo. Despite widespread scholarly interest, however, the operative logics of populism as an apparatus of affective production and capture have been overlooked. Taking insights from the affective and more-than-human turns, this thesis responds to calls for political geographers to engage in these discussions and proposes we understand populism through the metaphor of the resonance machine. The argument is made through the case of the nationalist populist party, the Sweden Democrats (SD), with the 2018 Swedish General Election – in which SD grew more than any other party – as my core focus. Adopting an affectively conscientious approach, I analyse the machinery, musterings and mobilisations that fuel populism’s momentum. The thesis constitutes the first book-length ethnographic engagement with SD, with novel and rich data acquired through time spent with campaigners and supporters between April 2018 and May 2019. The analytical value of understanding populism as machinic is shown through the discussion of three central themes. First, I shed light on the feelings, ideas, and deep stories that moved voters. Specifically, I indicate the nuances of distrust and nostalgia and show the importance of events in both the amplification and capture of affect. Second, I show how SD intentionally tapped into the ‘gut feelings’ of the electorate by harnessing branding tools to project authenticity. Third, I demonstrate how territorialisation occurred at sites of encounter between the party and the electorate – both at physical ‘hotspots’ and in the online media ecosystem. I reveal the importance of creating an imagined community and shared common sense, suggest this explains how populisms evolve from protest movements into publics, and indicate potential implications for the institutionalisation and maintenance of these movements in the future.