**Trader consensus centers on 78-80% turnout in Brazil’s October 4 presidential first round because this range aligns closely with the 79.05% recorded in 2022 and with pre-election analyst projections.** An electorate of 158.7 million registered voters, now older with a larger share over 70 (where voting is optional), combined with high rejection rates near 50% for both leading candidates, contributed to modest abstention pressure around 21%. Blank and null ballots added further drag on valid votes. Polarization encouraged strategic participation among core supporters while limiting broader enthusiasm, producing participation near the upper end of historical norms. A significantly different outcome would have required unusual last-minute mobilization or weather disruptions not observed in final reporting from the Superior Electoral Court.