Chapter 4 estimates the impact of another exogenous shock to incumbent capacity – changes in commodity prices. Brazil is one of the main producers of several commodities, such as coffee, bananas, oranges, and corn. Many municipal economies depend on rural agricultural production. Exploiting this diversified crop portfolio to build a municipal measure of changes in commodity prices, the chapter shows that commodity shocks have a strong impact on incumbency bias in rural municipalities. While negative commodity shocks deepen existing incumbency disadvantages, positive ones remove them. The results also indicate that commodity prices influence incumbency bias not by conditioning spending but through economic growth. This suggests that incumbency bias is partly driven by citizens’ informational limitations for discounting shocks. Brazilian mayoral elections demonstrate that offices with high policy scope but low capacity tend to experience an incumbency disadvantage, but that exogenous shocks to capacity can create heterogeneity in incumbency bias.