Recent studies have documented a shift from moderate political attitudes to more extreme attitudes at the ends of the political spectrum. This can be seen in Political Correctness (PC) on the left, and white identitarian (WI) attitudes on the 'Alt-Right' (AR). While highly covered in mainstream media, limited academic research has investigated their possible antecedents and psychological correlates. The current study investigated the prevalence and psychological predictors of these attitudes. Utilising a quota-based sample of 512 U.S. participants, we found that extreme political attitudes were associated with various personality traits, social media use, and upbringing. PC attitudes were associated with agreeableness, black-white thinking, social-media use, and perceived overprotective parenting. WI attitudes were associated with low agreeableness and openness, and high black-white thinking. Our results show that extreme left and right attitudes are separated by individual differences, and that authoritarianism can be seen on both the left and the right.