Populists govern more of the world’s countries than at any point in the past century, on both the right and the left. What they share is not an economic programme but a worldview that casts politics as a struggle between ordinary citizens and a self-serving establishment, a conflict that is zero-sum at its core. We show that exposure to this political environment leaves a durable imprint on citizens’ beliefs. Combining data on populist leaders with surveys of more than 260,000 respondents in 53 countries, we exploit within-country-survey-year variation across birth cohorts and find that greater exposure during early adulthood is associated with stronger zerosum beliefs later in life. The result is replicated in two independent surveys and across multiple measures of zero-sum thinking and perceived economic conflict and persists into respondents’ mid-forties. The associations extend to voting intentions: exposure does not predict support for populist parties overall, but it does predict support for ideologically extreme parties aligned with the populist rule experienced in early adulthood. The mechanism evidence provides little support for an economic-scarcity explanation and instead points towards a rhetorical channel, as populist rule features substantially more anti-elite rhetoric in two independent measures and more domestic zero-sum framing in United Nations speeches.