Mauro Mendes, the former Mato Grosso governor running under a broad coalition including União Brasil, holds a commanding lead in late-September 2026 polling for the state's two Senate seats, with 36% in first-preference votes and over 55% in consolidated mentions across surveys from Veritá and Quaest. His candidacy registration was approved by the TRE-MT in early September after minor documentation issues were resolved, removing any eligibility concerns. This incumbency advantage, combined with endorsements from over 100 mayors and strong name recognition, explains trader consensus assigning him the highest probability for first place ahead of the October 4 election. Lower probabilities for names such as Janaina Riva, José Medeiros, and Carlos Fávaro align with their more distant polling positions in the same recent surveys.