Janaina Riva holds the clearest edge for second place in Mato Grosso’s two-seat Senate race, consistent with recent polling that places ex-governor Mauro Mendes first and her ahead of the remaining field. Consolidated first-and-second-preference surveys from late August show Mendes in the mid-to-high 40s and Riva in the low-to-mid 30s, with José Medeiros, Pedro Taques, and Carlos Fávaro clustered well behind. High undecided shares (18–25 percent) and the dual-vote format keep the contest for runner-up fluid, as second preferences remain malleable. Official candidacies were confirmed after party conventions in early August, and no major late-breaking developments have yet reordered the mid-tier group. Traders’ assessment reflects Riva’s sustained polling advantage and name recognition among state legislators, while noting that further shifts in alliances or turnout among rural and interior voters could still narrow or widen the gap before the October 4 election.