It was a tougher line from Marois, who has so far suggested Couillard has no ideas about how to govern the province.
The CROP online survey was conducted March 12 to 16 and put the Liberals at 39 per cent support and the PQ at 36 per cent among respondents.
The same poll, which was done for Montreal La Presse, said two-thirds of respondents indicated they did not want a referendum on sovereignty and that roughly the same amount believed the PQ would hold a referendum if elected on April 7.
Persistent questions about Marois' sovereignty agenda has often derailed discussions of other issues such as the controversial secularism charter which the PQ had cited as a priority as the campaign began.
Marois insisted Tuesday her party's message is on track.
"I'm very satisfied with the game plan we have put forth," Marois told her only media availability of the day before heading off to prepare for Thursday's televised debate. "What concerns me, on the other hand, is returning to the old ways under the Liberals.
"Do you want to go back to what we knew with Mr. Charest — the same vision, the same team, the same perspective, the same ethical problems?"
She alluded to Couillard's relationship with Arthur Porter, who is currently facing corruption charges in connection with the construction of a Montreal superhospital. Marois also zeroed in on Couillard's decision to quit as health minister in 2008 to immediately join an investment fund that specialized in the establishment of private clinics.
While Marois attempted to question Couillard's integrity, she refused to respond to a question about alleged dealings between her husband and the Quebec Federation of Labour that were raised in testimony at the provincial corruption inquiry several weeks ago.
"The ethical track record of our government and our party is absolutely remarkable," was all she would say.
Couillard was asked at a news conference in Longueuil later in the day if he noticed a change in the campaign's tone given the poll results and Marois' focus on ethics.
"I detect a certain amount of worry, to say the least," said Couillard, who appeared annoyed by the questions about Porter.
"There is a change in the rhythm and the tone. I'm making the choice not to follow Mme. Marois on the tone she's adopted. It would be extremely easy for me (to do so). I don't do politics like that. I'll let the citizens judge for themselves."
Couillard focused on the economy on Tuesday and promised to achieve a zero deficit in the next year.
"This is not the time for cosmetic measures," he said. "We must take significant steps with regard to taxpayers and their ability to pay."
While he said a government led by him would control spending, Couillard added a Liberal regime would also give confidence to investors.
"We have a government that does not know how to generate economic growth," he said of the PQ.
Parti Quebecois candidates Nicolas Marceau and Pierre Karl Peladeau also took aim at Couillard, with Marceau dismissing his economic numbers and saying suggestions of investment growth under the Liberals are "ridiculous."
"The recent past has taught us that the only thing that grows quickly under the Liberals is debt and corruption," Marceau said.
Peladeau said the Liberals are using an old economic model that is based on infrastructure and going into debt.
The poll also indicated a drop in support to 13 per cent for the Coalition party, which received 27 per cent of the vote in the 2012 election.
Francois Legault, a former PQ cabinet minister and airline executive who co-founded the right-centre party in 2011, said he is "realistic" about the results.
"I have been through difficult periods before," he said in Granby. "My father died when I was 26 years old. At Air Transat, I wondered if we going to go bankrupt or if we would be able to pay the employees. I am able to take it.
"I will fight until the end to elect the most members to the legislature," said a dejected-looking Legault. "I am a realist."
He ruled out any switch to another party if the Coalition is hit hard on voting day.
"I have defended the third option for seven years," he said. "It's out of the question to abandon it. Out of the question to go with the PQ or Liberals."
Legault also took a shot at Couillard, who analysts suggest is benefiting from the drop in Coalition support, saying he can't get a straight answer from him about his stand on electricity rates or the development of wind farms.
"How much is he willing to spend to continue buying votes," Legault asked.
Legault pressed his message of giving a tax break to the middle class and vowed the Coalition would never allow any tax or fee to increase beyond the inflation rate for the next four years.
— With files from Canadian Press reporters Martin Ouellet, Melanie Marquis and Sidhartha Banerjee in Montreal, Julien Arsenault in Becancour and Etienne Fortin-Gauthier in Granby
Follow @nelsonwyatt @sidhartha_b @JulienArsenault @EtienneFG and @melmarquis on Twitter
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