Partisans who back illiberal measures in their benefit jeopardize democracy. We rely on original survey and focus group data from Argentina, a severely polarized nation, to explore important precursors of bottom-up support for backsliding. First, we show that partisans construct regime stereotypes, depicting fellow partisans as democratic and rivals as authoritarian. This offers fertile ground for justifications of exclusionary policies. Second, an experiment with random assignment to post-election scenarios describing a party’s landslide victory allows us to study whether partisan affect exacerbates emotional reactivity and/or shapes trust in democratic institutions in the face of victory/defeat. All Argentine partisans are emotionally reactive, whereas conditionally democratic attitudes are more salient among Kirchnerists/Peronists. We attribute this difference to the nature of partisanship. Unlike their rivals, who are mostly negative partisans, Peronists/Kirchnerists profess the strongest positive creed in the system. Elections can therefore turn into moments of existential angst, during which the idea of losing becomes particularly intolerable. Our analysis thus illuminates the conditions that render polarization harmful for democracy. If partisan beliefs about the reliability of elections or enthusiasm for democracy depend on victory, the door suddenly opens for leaders to manipulate feeble democratic commitments in the event of defeat.