Raymond Bachand, who held the finance portfolio untillast week, announced his entry at a news conference accompanied by a few MNAs.
Bachand's participation could add some ideological spice to the race.
He was the architect of the Liberals' proposed tuition hikes, which were heavily supported by small-c conservatives but bitterly opposed by progressives. They have now been cancelled by the new Parti Quebecois government.
"I'm the man who will help bring Quebec, in a unifying way, on the path to economic prosperity," Bachand said.
"My obsession is jobs."
In a subtle effort to distance himself from the Charest years, he also said the Liberals needed to become a party of debate and ideas once again — a role played by the party numerous times throughout Quebec history.
A common complaint about Charest is that the former premier was non-ideological to a fault, and had few political passions other than repelling Quebec independence.
Bachand will face stiff competition as Philippe Couillard, a popular former health minister, is all but certain to enter the race and become a potential front-runner.
It remains to be seen whether the party's federalist grassroots will hold Bachand's past against him; back in his early 30s he was a prominent figure in the PQ during the 1980 independence referendum.
Bachand sought to reassure Liberals that he is a committed member of the federalist family. Accompanying him at the event Friday was the widow of the late former premier Robert Bourassa.
He also spoke about his attachment to Canada. He said Quebecers had helped shape the country and that it was part of their heritage. He also spoke in English, in a message aimed at the party's Anglo base.
"I'm proud to be a Quebecer," he said, "but I'm also proud to be a Canadian."
He even cast his past as a bonus — as a sign he can be the candidate of change.
"Change?" he asked, rhetorically.
"Everyone knows that in the 1970s I worked for Mouvement souverainete-association and for the Parti Quebecois — but the world changed. The planet changed and the future needs of Quebec are not the needs of Quebec of the '60s and '70s. You need to adapt."