Epistemic hubris—the expression of unwarranted factual certitude—is a conspicuous yet understudied democratic hazard. Here, in two nationally representative studies, we examine its features and analyze its variance. We hypothesize, and find, that epistemic hubris is (a) prevalent, (b) bipartisan, and (c) associated with both intellectualism (an identity marked by ruminative habits and learning for its own sake) and anti-intellectualism (negative affect toward intellectuals and the intellectual establishment). Moreover, these correlates of epistemic hubris are distinctly partisan: intellectuals are disproportionately Democratic, whereas anti-intellectuals are disproportionately Republican. By implication, we suggest that both the intellectualism of Blue America and the anti-intellectualism of Red America contribute to the intemperance and intransigence that characterize civil society in the United States.