Politicians vary in both their competence and their policy preferences. We show that how voters trade off competence against ideological congruence has key implications for the type of representation incumbents provide. When voters privilege competence, they encourage trustee representation, and when voters emphasize ideological congruence, they encourage delegate representation. Selection on competence is most likely to occur when uncertainty about the policy preferences of politicians is minimal. A surprising implication of our analysis is that ideological congruence between incumbents and voters is not a necessary precondition for trustee representation to be rewarded at the ballot box.