The role of experts in politics has gained increasing visibility and has become further contested during the polycrises of the 21st century. Expert interventions across economic, social, health, and environmental domains are frequently linked to rising social polarization and debates over the democratic legitimacy of technocratic and scientific authority. This paper takes a step back to investigate, first, how citizens evaluate expertise, and second, what forms of expertise they consider legitimate in political decision-making. Using experimental evidence, it further examines the extent to which citizens' perceptions of expertise and independence are shaped by the issue positions held by experts. The findings reveal that while citizens broadly agree on abstract criteria for expertise, their evaluations diverge significantly when the issue positions of experts are revealed or inferred. These results align with motivated reasoning theory and social cleavage theory, shedding light on why expert involvement in politics becomes contentious when issues are politicized.