How is the use of political lotteries related to party development? This article discusses the effects of a lottery-based procedure used to distribute committee appointments that was once common across legislatures in nineteenth-century Europe. The authors analyze the effects of a political lottery in budget committee selection in the French Third Republic using a microlevel data set of French deputies from 1877 to 1914. They argue that the adoption and benefit of lottery-based procedures were to prevent the capture of early institutions by party factions or groups of self-interested political elites. The authors find that partial randomization of selection resulted in the appointment of young, skilled, middle-class deputies at the expense of influential elites. When parties gained control of committee assignments in 1910, selection once again favored elites and loyal party members. The authors link lottery-based procedures to party development by showing that cohesive parties were behind the institutional reform that ultimately dismantled this selection process. Lottery-based procedures thus played a sanitizing role during the transformation of emerging parliamentary groups into unified, cohesive political parties.