How do legislators build the reputations they use in bids for reelection? Do they use their personal reputations or associate with other legislators? And how do parties, coalitions, and institutions affect these decisions? Research on how electoral systems affect parties in legislatures frequently focuses on the extent to which electoral rules make legislators more or less ideologically convergent with respect to other members of the chamber—copartisan and not. However, finding equilibrium strategies is often possible only under restrictive institutional and spatial assumptions. Instead of viewing ideology spatially, we conceive of ideological reputations as currencies, used to purchase electoral support in transactions we liken to auctions. In our test of the model, we use bill cosponsorship patterns as an indicator of the reputations incumbents use to purchase electoral support. We show that under relatively common institutional conditions, legislators may have strong incentives to cultivate reputations they must share with their toughest electoral competitors.