Folk wisdom warns against making face value judgements, with warnings to “not judge a book by its cover”. However, reflecting the personalisation of politics and a strong visual emphasis in campaigns, it seems that voters' quick judgments based on candidate faces do play a role in explaining voting behaviour. The findings of experimental research indicate that voters’ behaviour is driven, to a significant extent, by  facial cues: i.e., the spontaneous trait inferences they perceive from the candidates’ faces, such as their competence.

This study extends this literature by examining which candidate traits voters infer from facial cues and how these explain electoral behaviour. It does so through an original survey experiment with a representative sample of 747 Portuguese voters who evaluated real-world images of mayoral candidates from Portuguese local elections. The experimental design combines controlled facial stimuli with systematic voter assessments, allowing a comprehensive analysis of voter heuristics derived from candidates’ facial traits. The study thus contributes empirically to the broader discussion on the normative implications of appearance-based voter judgments in democratic elections.