Recent studies in democratic countries suggest that voters generally prefer candidates with specific personal attributes, such as being female and young. However, some of these patterns cannot necessarily be explained by voters’ expectations of candidates’ competence. Building on a growing body of literature that addresses populist attitudes as an important factor influencing voters’ political preferences, this study hypothesizes that candidates’ personal attributes shape voters’ perceptions of their populist attitudes and that such perceptions mediate the relationship between personal attributes and voter preferences. A conjoint experiment conducted in Japan showed that several personal attributes substantially influenced candidates’ perceived anti-elitism and people-centrism. An additional experiment to disentangle causal mechanisms suggested that, albeit inconclusive, young candidates were more likely to be preferred because of voters’ expectations of their populist tendencies. Methodologically, this study illustrates advancements in the conjoint experiment design to elucidate causal mechanisms, with a careful discussion of necessary assumptions.