>The present research pursues two broad and complementary goals. The first goal is to establish solid evidence for a possible relationship between populist attitudes and belief in conspiracy theories. The second (and related) goal, then, is to test whether populist attitudes are associated with conspiracy beliefs in particular, or rather, credulity of unsubstantiated epistemic claims in general. Together the studies presented here provide evidence for populist gullibility, which we define as an increased tendency for people who score high on populist attitudes to accept unsubstantiated epistemic claims as true, including nonpolitical ones (see also Forgas & Baumeister, 2019). So now you know why agents of the left are pushing such ideas as the flat earth, alien abductions, or that Americans never walked on the moon. Such nonsense has a dual function -- to make people uncertain about what is real, and to discredit them. This study attempts to link what is now being called "populism" by the left -- i.e., popular support for nationalist and conservative points of view -- with crazy conspiracy theories. Liberals have a couple of quaint but false beliefs: that conservatives are not as intelligent as they are, and that conservatives hold crackpot theories. Both liberal beliefs have been demonstrated to be untrue.