Why are women under-represented even in democratic and egalitarian countries? Previous research considers either demand-side or supply-side explanations. We integrate both perspectives in a least-likely case for the under-representation of women, namely the municipal councils in Denmark. The data is from a candidate choice conjoint experiment, a survey among potential candidates and data on the actual pool of nominated candidates. On the demand-side, we show that there is no pro-male bias in general or in combination with other candidate traits nor that traits evaluated positively by voters appear more frequently among actual male candidates. On the supply-side, we find that women are less likely to be interested in running for political office. This is primarily because women assess
their own political qualifications significantly lower than men. The gender imbalance is therefore driven by an under-supply of female candidates. This suggests that we should focus more on supply-side factors to overcome the gender imbalance.