Using an experimental approach, this chapter tackles the endogeneity problem of leader effects and disentangles the relationship between political and apolitical factors in the formation of judgments on political leaders: to what extent are evaluations of leaders the product of political considerations and to what extent are they solely based on their character traits? A second objective of the chapter is to analyse the institutional effects of parliamentary and presidential elections on the influence of character assessments on vote choices. The results of three experiments conducted in France, Germany, and Sweden suggest that perceptions of character traits are heavily influenced by the political assessments of candidates. Supposedly apolitical evaluations of political leaders will then often have a political foundation. In addition, the experiments revealed an institutional effect indicating a stronger influence of leader traits in presidential elections than in parliamentary elections.