Most scholars agree that members of Congress are strongly motivated by their desire for reelection. This assumption implies that members of Congress adopt institutions, rules, and norms of behavior in part to serve their electoral interests. Direct tests of the electoral connection are rare, however, because significant, exogenous changes in the electoral environment are difficult to identify. We develop and test an electoral rationale for the norm of committee assignment “property rights.” We examine committee tenure patterns before and after a major, exogenous change in the electoral system—the states' rapid adoption of Australian ballot laws in the early 1890s. The ballot changes, we argue, induced new “personal vote” electoral incentives, which contributed to the adoption of “modern” congressional institutions such as property rights to committee assignments. We demonstrate a marked increase in assignment stability after 1892, by which time a majority of states had put the new ballot laws into force, and earlier than previous studies have suggested.