Bernard Drainville said he will officially launch his campaign next Sunday in his Montreal-area riding of Marie-Victorin.
Drainville, 51, picked up his candidacy papers at PQ headquarters and said he made the decision to run after a long period of reflection.
The proposed values charter dominated Quebec's political scene in the months preceding last April's election.
It died when the Liberals stormed to victory.
The controversial project introduced in the fall of 2013 would have banned public employees from wearing overt religious symbols in the workplace.
While some polls suggested the charter was popular with a majority of Quebecers, it also drew outrage.
Opponents took to the streets to denounce the idea and even past PQ premiers Lucien Bouchard and Jacques Parizeau said it went too far.
Former cabinet minister Martine Ouellet is the only other declared candidate so far in the race to succeed Pauline Marois, who quit after the election.
Media baron Pierre Karl Peladeau, who will likely vault into front-runner status if he runs, has not yet said if he will take the plunge.
The new PQ leader will be known next May.
Stephane Bedard has been interim leader since Marois's resignation.
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