Rui Costa (PT) commands an 88.5% implied probability for first place in Bahia’s October 4 Senate election, driven by consistent polling leads in late-September surveys from AtlasIntel, Quaest, and Real Time Big Data. These place him at 23–28% in valid votes for the two-seat contest, ahead of running mate Jaques Wagner (PT) at 17–24%, with João Roma (PL) and incumbent Angelo Coronel (Republicanos) clustered further back. Costa’s edge stems from his profile as former governor and recent federal minister, backed by the PT-led coalition and high statewide name recognition. The remaining field trails at low single digits or below, aligning with the sub-2% prices on Wagner and Coronel for the top spot. With voting two days away, the market consensus tracks the latest polling trajectory without notable late shifts reported.