this article has two main objectives. the first one is to create a profile of senators' substitutes, compared to the elected senators. the second objective is to investigate the substitutes' political performance, with the intent of evaluating the impact of their actions on both the functioning of the senate and their relationship to the executive power. we suggest that, because they are not directly elected, they are selected to work on difficult tasks, especially those that could bring negative political effects to the senators, which depend on the electorate's vote. we also found that the substitutes give a bit more support to the presidency, particularly observed in right wing parties coalitions.