Flávio Bolsonaro leads the Polymarket for second place in Brazil’s October 4 first round because he is the consolidated Liberal Party nominee and primary right-wing challenger to incumbent Luiz Inácio Lula da Silva. Recent polls, including Quaest and Datafolha surveys from July, place him in the mid-to-high 20s to low 30s, well ahead of fragmented alternatives such as Renan Santos (Mission Party) or other listed names. Lula’s polling lead in the mid-to-high 30s to low 40s implies he is viewed as the likely first-round frontrunner, leaving Bolsonaro positioned to capture the bulk of opposition support. A May–June scandal involving leaked audios linking Bolsonaro to a fraud investigation temporarily pressured his numbers, yet subsequent surveys show resilience and only modest erosion. Party conventions in July formalized the main candidacies, while rising undecided voters and rejection ratings for both leading figures have kept the field otherwise dispersed. These dynamics explain the wide gap between Bolsonaro’s implied probability and the single-digit shares assigned to remaining contenders.