The Socialist Party's upcoming closed primary in mid-October 2026, open to PS militants and Place Publique allies, remains the central driver of trader sentiment, with no candidate yet consolidating broad support across internal factions. Recent party votes in July formalized this timeline and rejected a wider left-wing contest, while declarations from figures like Karim Bouamrane and positioning by Raphaël Glucksmann, Boris Vallaud, and Olivier Faure have kept the field fragmented. Historical precedent of contested socialist nominations and the absence of decisive polling or endorsements within the "pôle socialiste" sustain a wide distribution of implied probabilities. Late-campaign alliances, primary debate performances, or shifts in left-wing coalition dynamics ahead of the 2027 presidential vote could still reorder the field before ballots close.