Opposition could reach 43 senators in 2027, polls indicate

The opposition bench in the Federal Senate could jump from the current 34 to 43 senators starting February 2027, according to a survey based on electoral polls registered with the Electoral Justice. That number would give the bloc a simple majority in the House, but it would not reach the votes required to approve constitutional reforms or to remove Supreme Federal Court (STF) justices.

Bench growth and control of a simple majority

The projected rise to 43 senators would place the opposition above the 41 votes needed for an absolute majority. This level ensures the election of the Board of Directors, the presidency of thematic committees, the approval of ordinary bills and the validation of nominations to embassies, regulatory agencies and STF seats.

If President Luiz Inácio Lula da Silva wins, the scenario drawn by the polls indicates a more hostile environment for the Palácio do Planalto. Besides the need to negotiate nominations and concessions with the Centrão, a simple majority is enough to launch parliamentary inquiry committees, such as the CPIs on Banco Master and Lulinha.

Vote requirements for constitutional amendments and STF impeachment

Despite the numerical advance, the projections show the opposition bloc would remain far from the highest voting thresholds. For the approval of Constitutional Amendment Proposals (PECs), 49 votes are needed in two rounds, which would require the government or the opposition to negotiate with centrist and right‑wing parties.

To convict and remove Supreme Court justices through an impeachment process, the Constitution demands the support of two‑thirds of the Senate, equivalent to 54 parliamentarians. Even in a hypothetical scenario where all 17 senators classified as swing voters sided with the opposition, the total would reach 52 votes, two short of the indispensable number.

Party competition among PL, MDB and PT

The Liberal Party (PL) emerges with the highest number of competitive candidates for the renewal of two seats per federative unit, registering 11 affiliates who lead or are tied for first place in the polls. MDB follows with 8 candidates in the same situation, while PT totals 7.

Adding the seats that are not up for election and whose mandates run until 2031, the projection indicates PL will reach 20 senators in 2027. PT is expected to have 10 representatives in the House at the start of the next legislature.

STF ministers' reactions to the electoral debate

The promise by candidates to pursue impeachment of Court members sparked statements from within the Court itself. Senior justice Gilmar Mendes said the proposal has electoral appeal but is a mistake given procedural difficulties and the institutional behavior of the Powers. Mendes had already issued a monocratic decision in December 2025 suspending parts of the Impeachment Law and limiting the filing of accusations to the Attorney General's Office.

STF president Edson Fachin also spoke during a National Justice Council session, noting that while criticism of the Judiciary is legitimate, the political exploitation of abuse allegations represents populism against institutions.

Information from Poder360, Estadão, Gazeta do Povo.