There have been multiple reports that the former police chief has agreed to run for the new Coalition for Quebec's Future, giving the third-place party a huge boost as it tries to make the Liberal government's track record on corruption a key issue in the campaign.
The party is expected to confirm his candidacy as early as Sunday morning.
Duchesneau was hired by the Liberals in 2010 to investigate allegations of corruption and collusion in the construction industry. His report, which he leaked to the media because he felt the government would ignore it, claimed the construction industry was bilking the public purse and using some of its cash to illegally fund political parties.
News of his anticipated candidacy has thrust corruption to the forefront of the election campaign, something Charest tried to avoid as he presented his party as the choice of stability and economic growth.
Charest took pains Saturday to show he wasn't concerned about suggestions Duchesneau could shift the electoral landscape.
"It's an election campaign and during an election campaign there will be opponents," he said at a news conference north of Montreal.
The premier defended his government's record, sticking to an earlier assessment that gave his government eight-out-ten in its efforts to tackle corruption.
"I have no hesitation in saying that this is the grade we get, that the work we did is substantial," he said, adding that Duchesneau's work was part of a much larger team effort in his government's fight against corruption.
Charest said his government followed through on many of Duchesneau's recommendations, including setting up an inquiry into the construction industry.
Meanwhile, the Parti Quebecois confirmed a high-profile candidate of its own on Saturday.
Jean-Francois Lisee, a popular columnist and onetime adviser to former PQ premiers Jacques Parizeau and Lucien Bouchard, called for anyone opposed to the Liberals to unite behind the PQ banner.
A key player in the 1995 referendum, Lisee wouldn't commit to holding another in the early stages of a PQ mandate. But he said the Harper government's policies were helping to promote the cause.
"I think there will be a time when Quebecers will say, 'enough is enough, it's time to go,'" he said in Montreal.
"If the Liberals or the Coalition are in power they will not have that choice. If the PQ is in power, they will have that choice."
For his part, Coalition leader Francois Legault also courted the sovereigntist vote on Saturday as he promised more funding for the arts.
Legault, a former PQ minister who promises to shelve the nationalist question for ten years, said he would make sure to preserve Quebec culture and urged sovereigntists to vote for his party.
"You don't need to be a sovereigntist to love our culture and want to promote our culture," Legault said in Quebec City.
"I also invite those who were separatists and those who still are to ask: 'Wouldn't it be better to concentrate on promoting our culture rather than waiting for sovereignty's big night?'"
Also on HuffPost