Couillard continued to hammered away on Saturday at a theme that has been central to his campaign: the risk of another referendum if the Parti Quebecois gets a majority government.
By his count, Quebec would lose $16 billion a year, including $9 billion in equalization payments, if the province were to break away from Canada.
PQ leader Pauline Marois has previously acknowledged sovereignty could lead to five years of difficulty, but Couillard argued it would be more like a decade.
"It would lead to years of major disruption in the public service, in Quebec, in Quebec society," Couillard said while campaigning in his home riding of Roberval.
In focusing on sovereignty's economic fallout, Couillard took a page from the book of his predecessor, former Liberal chief Jean Charest.
Without setting out a timeframe, Couillard said his goal is to ensure that Quebec stops receiving equalization payments, a federal program which redistributes wealth across the country.
"We are a free people, we are a happy people," he said.
"I see no reason to deprive Quebec of Canadian citizenship. "
Marois, meanwhile, had a warning of her own for Quebec voters on Day 18 of the election.
She said a Liberal government would mean a return to corruption and turmoil under Charest, before the PQ took power in 2012.
"As Liberal leader, Philippe Couillard must apologize for what his party has done to our institutions," she said in Riviere-du-Loup.
"He must take responsibility on behalf of the Liberal Party for the most painful crisis of confidence that Quebecers have known."
Marois also tried to make the case that Quebec solidaire, a rival sovereigntist party, should focus its attention on Couillard rather than the PQ.
"When Quebec solidaire attacks us, they are attacking the wrong target," Marois said.
Marois said the PQ and Quebec solidaire are both progressive and pro-Quebec independence and must work together to avoid a Liberal government.
Although the social-democratic party holds only two seats in the Quebec legislature, polls suggest the party's popularity has climbed in recent weeks.
Quebec solidaire could steal away votes from the party's left-leaning voters in the April 7 election, potentially handing close ridings to the Liberals.
David has argued the PQ shifted its policies to the right after taking government in 2012.
She has also repeatedly slammed the PQ candidacy of media mogul of Pierre Karl Peladeau, saying a Quebec solidaire member would never sit by his side in the province's national assembly.
On Saturday, Marois said her party remains committed to improving social programs but must grow the economy to have the revenue to do so.
"I think Quebec needs to be stronger economically," she said.
- with files from Alexandre Robillard in Roberval and Martin Ouellet in Riviere-du-Loup
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