In Brazil’s 2026 Senate contest for Rio de Janeiro’s two seats, a crowded field of more than a dozen candidates has produced evenly matched trader odds, with no one exceeding 50% implied probability for first place. Early polling shows fragmented support, led by Benedita da Silva at roughly 11% followed by Marcelo Crivella near 8%, amid 22% undecided voters and high rates of blank or null ballots. Flávio Bolsonaro’s decision to run for president rather than seek reelection has opened the race, while party lists from PL, PT, Republicanos, and smaller groups remain fluid. This dispersion, combined with the October 4 first-round vote and limited name recognition for most contenders, keeps probabilities tight and sensitive to late shifts in alliances or turnout patterns.