Less than one day into the ring, Jacques Duchesneau has already showcased his larger-than-life personality and sparked further doubts about his ability to be a team player in the world of politics.

Speaking to a Montreal radio station, the ex-cop said he would be the "conductor" – the "chef d'orchestre" – of the Coalition Avenir Québec's anti-corruption effort. In particular, Mr. Duchesneau said he would oversee a number of departments in Quebec City that are part of the fight against corruption, such as municipal affairs, natural resources, transport and public safety, including appointing ministers.

The statement by the star CAQ candidate, recruited on Sunday as a potential "game-changer" in the campaign, quickly threatened to undermine the leadership of party leader François Legault.

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"I will be deputy premier," Mr. Duchesneau told radio station 98.5 FM on Monday morning. "It's out of question that I would be a deputy premier like we had 30 years ago, which is a bit of an honorific title. I have responsibility over those departments, with the possibility of naming the ministers. Overall, I am responsible for the fight against corruption, like a conductor," he said.

The CAQ quickly clarified Mr. Duchesneau's statement, with the party stating on its Twitter feed that Mr. Duchesneau would only be "consulted on nominations linked to the fight against corruption and collusion," but would not have the final say over them.

"There will be only one boss," Mr. Legault told reporters Monday.

Mr. Duchesneau also stunned reporters on Sunday when he said that he had conducted "due diligence" over the CAQ and Mr. Legault before joining the party. According to La Presse, Mr. Duchesneau tasked two lawyers, including his son, to look over the party's books and its various candidacies.

Normally, in politics, the party screens its new recruits.

Quebec Liberal Leader Jean Charest said his party's books are open and he was surprised to see that a candidate for another party would task a lawyer to look at its books before jumping in.

He also poked fun at the notion that Mr. Duchesneau would have more power in a CAQ government than Mr. Legault, who is a prolific user of social media in this campaign.

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"If I understand correctly, François Legault will run the Twitter account and organize cocktail fundraisers, while Jacques Duchesneau will run the rest of the government," Mr. Charest said.

He also rejected the CAQ's analogy that Mr. Duchesneau would be "Quebec's Eliot Ness," in reference to the man who brought down Al Capone in Chicago.

"Eliot Ness was a police officer, not a politician," Mr. Charest said.

According to Parti Québécois leader Pauline Marois, Mr. Duchesneau's ego is turning out to be a serious problem for CAQ leader François Legault. She said the comments reflect improvisation within the CAQ, an indication that Mr. Legault isn't ready to govern the province.

"What is going on right now isn't very serious. It is total improvisation," Ms. Marois said. "It is amateurish and it is also a lack of understanding of how government works."

The naming of ministers is the premiers' prerogative and a deputy premier wouldn't have say over the matter, as Mr. Duchesneau claimed, she said.

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Ms. Marois said that by naming candidates to ministerial positions before he was even elected, Mr. Legault was counting his chickens before they hatch.

"First you wait until the election is over," she said. "Then you name a cabinet based on regional representation, based on a balance between men and women. "

The PQ leader said she had at least four or five candidates who could easily become finance minister or cultural minister. But Ms. Marois refused to give names, saying that people simply had to look at the resumes of her candidates to determine who they are.