The Senate has 81 members, serving an eight-year term of office. There are three senators from each of the country's 27 federative units, the Federal District and the 26 states. Elections are staggered so that either a third or two-thirds of senators are up for election every four years. The most recent election took place in 2022, where one-third of the Senate was elected.
Elections are held under the first-past-the-post and block voting systems. In years when a third of members are up for election, voters can cast only one vote and the candidate who receives a plurality of votes within their state is elected. In years when two-thirds of members are up for election, voters can cast two votes. People can not vote for the same candidate twice, but each party can field up to two candidates in each state. The two highest-placed candidates in each state are elected.
Following independence, in 1822, Emperor Pedro I ordered the convocation of a Assembleia Geral Constituinte e Legislativa (Legislative and Constituent General Assembly) to draft the country's first Constitution. Following several disagreements with the elected deputies (which included representatives from present-day Uruguay, then part of the Brazilian Empire under the name of Província Cisplatina), the Emperor dissolved the Assembly. In 1824, Pedro I implemented the first Constitution which established a legislative branch with the Chamber of Deputies as the lower house, and the Senate as an upper house.
The first configuration of the Senate was a consulting body to the Emperor. Membership was for life and it was a place of great prestige, to which only a small part of the population could aspire. The original Senate had 50 members, representing all of the Empire's provinces, each with a number of senators proportional to its population. In addition to these elected senators, daughters and sons of the Emperor aged at least 25 were senators by right.
The elected members of the Senate had to be at least 40 years old and have an annual income of 800,000 contos-de-réis, which limited candidates to wealthy citizens. Voters also faced an income qualification. Voting in an election for the Senate was limited to male citizens with an annual income of at least 200,000 contos-de-réis. Those who qualified for this did not vote directly for senators; instead, they voted for candidates to be Senate electors. To be a Senate elector required an annual income of 400,000 contos-de-réis. Once elected, these electors would then vote for senator. The election itself would not result in a winner automatically. The three candidates receiving the most votes would make up what was called a "triple list", from which the Emperor would select one individual that would be considered "elected". The Emperor usually chose the candidate with the most votes, but it was within his discretion to select whichever of the three individuals listed.
Following the adoption of the 1824 Constitution, the first session of the Senate took place in May 1826. The Emperor had repeatedly delayed calling the first election, which had led to accusations that he would attempt to establish an absolutist government.
The Proclamation of the Republic in 1889 ended the Brazilian Empire in favor of the First Republic. The 1891 Constitution was then adopted, transforming Brazil's provinces into states and the Senate into an elected body. This was retained under later constitutions, including the current 1988 Constitution. Now known as the Federal Senate, it resembles the United States Senate in that each state has the same number of senators.
Palácio Conde dos Arcos, seat of the Imperial Senate in Rio de Janeiro, then Brazil's capital.
^"Senado Federal completa hoje 185 anos". R7 (in Portuguese). 6 May 2011. Retrieved 22 May 2012. O Senado Federal foi criado com a primeira Constituição do Império, outorgada em 1824, inspirado, primeiramente, na Câmara dos Lordes da Grã-Bretanha. Sua primeira reunião ocorreu em 6 de maio de 1826..