The upcoming September 27 partial renewal of 178 Senate seats keeps SER probabilities tightly clustered between 59-64, as the group defends roughly 30-31 of its current 64 seats against competition from the Union Centriste (59 seats) and other lists. Indirect voting by grands électeurs favors parties with strong municipal and departmental roots, where Socialists have consolidated positions following recent local contests, while right-leaning and centrist groupings seek incremental gains in targeted departments. Limited RN inroads and left-wing fragmentation add uncertainty without clear dominance, and historical patterns of modest net shifts in staggered Senate elections reinforce the narrow range. Developments such as unified candidacies, last-minute alliances, or turnout variations among local officials in key series-2 departments could produce separation in the final weeks.