São Paulo’s Senate race for two seats on October 4 remains fragmented after candidate registration closed in mid-August, with recent Ideia/ACSP polling showing Simone Tebet, Marina Silva, Guilherme Derrite, André do Prado, and Ricardo Salles clustered in the top tier and no candidate exceeding 27 percent. The single-round, two-vote system amplifies this dispersion, as voters split preferences across established figures from MDB, REDE, PP, PL, and NOVO alongside lesser-known names. Trader consensus on Polymarket reflects this uncertainty, with leading probabilities clustered near 50 percent and only modest separation for Silva and a handful of others. Late-campaign alliances, turnout among urban and interior voters, and any last-minute party coordination could consolidate support and shift the ordering before election day.