Left-wing and ecologist parties have formed strategic alliances across France to block right-wing candidates in the upcoming second round of municipal elections.Incumbent Jean-Luc Moudenc faces a narrow challenge in Toulouse from Fran'ois Piquemal, while former mayor Alain Carignon leads a polarized race in Grenoble.Additional coalitions have emerged in Villepinte and Champs-sur-Marne as opposition groups merge lists to prevent victories by center-right and conservative rivals.