Paris Saint-Germain beat Toulouse 2-1 to keep pace in the title race, and remain one point behind Marseille.
Nancy midfielder Julien Feret opened the scoring with a curling shot in the 34th minute.
But Ayew equalized from close range on the stroke of half-time.
Ayew had his cross parried by goalkeeper Damien Gregorini in the 87th but the Ghana winger pounced on the loose ball to score the winning goal.
Rennes beat Lens 2-0 Saturday to take the provisional lead, one point clear of Lille which hosts fourth-place Lyon later Sunday.
In Paris, Sylvain Armand scored in the 28th after first chesting down a clearance from the Toulouse defense. PSG doubled the lead in the 38th with an own goal from Adrian Gunino who deflected a shot from Mathieu Bodmer.
Franck Tabanou scored a consolation goal for Toulouse in the 62nd.
Toulouse midfielder Paulo Machado missed a penalty kick in the 17th after Armand fouled Moussa Sissoko.
On Saturday, it was: Sochaux 0, Montpellier 0; Saint-Etienne 0, Nice 2; Valenciennes 0, Lorient 0; Arles-Avignon 1, Brest 1; Monaco 2, Caen 2; and Bordeaux 3, Auxerre 0.