In three studies (two preregistered; total n = 3,490 ideologically balanced U.S. adults), we examined attitudes toward 40 institutions, organizations, and groups of professionals (e.g., journalists, scientists, the Supreme Court, the World Health Organization, professors, police officers, doctors, the Catholic Church, banks, pharmaceutical companies, psychologists, Facebook), and tested the associations between (1) perceived ideological slant (the percentage of people in those institutions that lean politically left or right), (2) perceived politicization (the extent to which political values impact the work they do), and (3) public trust and willingness to support and defer to the institution’s expertise. Higher congruence between participant ideology and perceived institutional slant predicted higher trust and deference. And higher perceived politicization of institutions consistently predicted lower trust, often with large effect sizes. Similar patterns were observed between institutions, such that the institutions perceived as the most politicized were also the least trusted, with a very large effect, r = -0.76. Studies 2 and 3 found that perceived politicization also predicted lower support and willingness to defer to institutions’ expertise. Across studies, these negative relationships were observed among both participants who shared and opposed the institution’s ideological slant. In other words, even left-leaning participants were less trusting and less willing to support and defer to left-leaning institutions that appeared more politicized, and even right-leaning participants were less trusting and less willing to support and defer to right-leaning institutions that appeared more politicized. Studies 2 and 3 attempted to experimentally manipulate perceived politicization and failed to do so. We thus post this preprint in hopes of initiating discussion of these findings and identifying promising avenues for future research and possible interventions.