PL leads the market with an 85.5% implied probability due to its alignment with Flávio Bolsonaro’s presidential bid and Jair Bolsonaro’s endorsement, which boosts candidate recruitment and right-leaning turnout in key states. Two-thirds of the 81 Senate seats (54 total) are contested on October 4 via plurality block voting, two per state and the Federal District. Recent presidential polling shows the PL ticket competitive nationally, reinforcing expectations that the party will secure the largest bloc. Centrist parties such as MDB and PSD trail at single-digit probabilities, reflecting weaker statewide organizations and limited coattail effects. No major late shifts in alliances or candidate filings have altered the consensus in the past month.