Outgoing Quebec Justice Minister Jean-Marc Fournier has become the interim leader of federalist forces in the province.
Mr. Fournier is expected to lead the Quebec Liberal party for several months until a permanent successor to Jean Charest is chosen.
Mr. Fournier served as an aide to ex-federal Liberal leader Michael Ignatieff and has been a frequent critic of the Harper government's justice policy.
Mr. Charest announced in Quebec City today that the party's caucus had unanimously approved Fournier's appointment.
Mr. Fournier is warning he will not be steamrollered by the Parti Québécois minority government if it tries to pass its most controversial measures while the Liberals are leaderless.
Mr. Fournier will remember how the federal Liberals were forced to roll over on key votes in recent years because it was afraid of provoking an election.
He said he will fight the PQ's plans on language and sovereignty.
"All measures looking to divide Quebecers, or all measures that aim at separating Quebec from Canada, will be vigorously fought," said Mr. Fournier, a lawyer by training.
He said he was assuming his new role with humility — paying tribute to the Liberal party's legacy in shaping the history of Quebec.
The leadership post became vacant last week after Mr. Charest announced his resignation.
Mr. Charest said he will leave political life once he transfers power over the premier's office to the PQ's Pauline Marois next Wednesday.
His resignation after 14 years at the party helm was prompted by last week's election defeat.
His Liberals' loss was narrower than expected. Despite three terms in government, numerous ethics controversies and a split in the non-separatist vote, Mr. Charest's troops lost by only four seats and less than one percentage point of the popular vote.
But the premier also lost his own riding for the first time ever. He said he spoke to his family about his political future and they all agreed he should move on after 28 years in public life.
The outgoing premier appeared in good spirits as he prepared for a final caucus meeting Wednesday. On his way in, Mr. Charest cracked jokes in a scrum with reporters.
When asked whether he would continue weighing in on political debates, he quipped he would "rather be a grandfather than a mother-in-law" — the latter being a pejorative term in Quebec politics that refers to former leaders who second-guess their successors. The 54-year-old is about to become a grandfather.
One of his possible successors is Finance Minister Raymond Bachand.
He is the architect of the government's attempt to hike university fees and his candidacy could be popular with small-c conservatives. However, his distant past in the employ of René Lévesque's PQ could cost him votes among the party's resolutely federalist grassroots.
The former business executive, university professor and public servant said he has received encouragement to run from his family and colleagues. He said he wants the party to have a successor in place quickly, before next year's budget, so the opposition can be ready to block the PQ's "disastrous" policies.
Another potential contender is Philippe Couillard, the popular former health minister.
A neurosurgeon and onetime hospital administrator, Mr. Couillard has been appointed by the Harper Tories to the Security Intelligence Review Committee, the body that monitors CSIS, Canada's spy agency.
Mr. Couillard has said he is considering entering the race.