Flávio Bolsonaro’s first-round lead in Brazil’s October 4 presidential election has driven trader consensus toward an 84% implied probability of victory in the October 25 runoff against incumbent Luiz Inácio Lula da Silva. With 47% of valid votes to Lula’s 45%, neither candidate secured a majority, but historical patterns since the return to democracy show no first-round runner-up has won the second round. Flávio has moved quickly to consolidate right-wing support through endorsements from eliminated candidates such as Ronaldo Caiado and outreach to centrist legislative blocs, while the broader Liberal Party performance in congressional and gubernatorial races has strengthened the movement’s institutional position. Lula faces a narrow window to mobilize turnout and undecided voters amid a polarized electorate.