Partisans --- voters who feel closer to one party over the other --- rarely vote for opposition party candidates. In contrast to existing work, I argue that two critical constituency-level factors jointly shape a partisan's likelihood of voting for a candidate from the other party when desirous of more public infrastructure. The first is partisan geography: partisans have an incentive to vote for a similar or better opposition politician when they live side by side with her supporters in a community (i.e., partisan nonsegregated areas) because politicians cannot exclude them from the provided benefits. Second, voters only have an incentive to cross party lines in competitive electoral districts because their vote can be pivotal in selecting and sanctioning an opposition politician. In other electoral settings, partisans have few incentives to vote for opponents because they either do not expect to benefit from the goods they will provide or believe that their vote is not essential (or both). I find support for my hypothesis and proposed explanation using data from a conjoint experiment alongside survey responses of citizens (N=2,020) located in a stratified, representative sample of electoral districts in Ghana.