Support for populist and authoritarian regimes is rising worldwide, despite evidence that they tend to underperform economically. To examine the role of (mis)perceptions of regime performance as drivers of political attitudes, we conducted a survey experi- ment during Argentina’s 2023 presidential elections. At baseline, optimistic beliefs about the performance of populist and non-democratic regimes were widespread, and correlated with support for these regimes. When exposed to randomly assigned informational treat- ments challenging optimistic views about right-wing populism or autocracies, individuals significantly adjusted their beliefs and their support for candidates associated with such regimes. We explore the impact of different information sources, showing that scientific sources and newspapers are more influential than social media. Although individuals ap- pear to adjust their beliefs and attitudes in response to credible information, we find that information countering people’s beliefs reduces their demand for additional information on regime performance, consistent with an important role for motivated reasoning.