About this election
The 2018 Senate election, held with the general election on 7 October, produced the largest turnover of Brazil's upper house in decades. With two of the three seats in each state up for renewal, roughly half of all sitting senators were replaced, as the anti-establishment mood swept out incumbents and lifted new and right-wing figures. The Brazilian Democratic Movement (MDB) remained the largest single bloc but emerged diminished in a more fragmented and conservative chamber.
The Federal Senate has 81 members — three for each of the 26 states and the Federal District — serving eight-year terms. The chamber is renewed in alternating cycles of one-third and two-thirds: in 2018 two seats per state (54 in total) were contested simultaneously by first-past-the-post, with voters casting two votes. Because senators represent whole states equally regardless of population, the Senate gives disproportionate weight to smaller, often more rural states, and its composition is decisive for confirming appointments and constitutional change.
As with the Chamber, the Senate races were caught in the wider anti-incumbent wave and the polarisation of the presidential contest. Several prominent veterans were defeated, and the elections returned a crop of newcomers, including allies of Jair Bolsonaro and figures associated with the agribusiness and security lobbies, alongside survivors of the traditional parties.
Counting both the newly elected senators and those not up for election, the resulting 81-seat chamber was led by the MDB with 12 seats, followed by the PSDB (9), the PSD (7), the PT and Democrats (DEM) with 6 each, and the Progressives, the Sustainability Network (REDE) and Podemos with 5 apiece; Bolsonaro's PSL entered with 4. The remainder was spread across more than a dozen smaller parties, leaving no bloc near the 41 needed for a majority.
The fragmented Senate, like the Chamber, obliged the new Bolsonaro government to build shifting majorities through the "centrão". The upper house's power over appointments — including to the Supreme Federal Court — and over constitutional amendments made it a crucial arena throughout the term, and its conservative tilt foreshadowed the even stronger right-wing presence that would follow the 2022 election.
Compiled and reviewed by Bartłomiej Paruzel, Election Data Analyst, from official results. See our data methodology.