The study of individual differences and leadership has a long and contentious history. There are many theories detailing the associative relations between traits and leadership, but less consider leader development. In demanding economic and political times, organisations need to be able to develop individual people as leaders. Social Potency was used as a representative measure of leadership potential, as people who display this trait share many of the characteristics required for suitability and likening of the leader role. Traits examined as potential predictors included Intelligence, Achievement Striving, Stress Reaction, and Control. Using the population based, longitudinal Minnesota Twin Family Study, it was possible to investigate which specific traits predicted a change in Social Potency between the ages of 17 and 25. The sample was split into two subsamples, for exploratory and confirmatory purposes. This study used regression analysis to assess the various contemporaneous and developmental relations between the specified traits and Social Potency. Moderator variables were also examined. The list of individual differences when used as a set of predictors of change in Social Potency accounted for around 39% of the variance in the model in both subsamples. The individual traits themselves had differing predictive contributions to the development of Social Potency, none of which stayed consistent across both subsamples. Additionally, intelligence moderated the Achievement Striving- Social Potency relation in both subsamples. Overall, the results suggest that although traits are important to leader development this may not be due to their individual contributions, but due to their interactions with each other.