SHERBROOKE, Que. -- Liberal Leader Philippe Couillard says his opponents will pay at the polls Monday for what he is calling their insult-laden campaigns.

Couillard accused Parti Quebecois Leader Pauline Marois on Thursday of taking the low road on the campaign trail and said voters are starting to tune out because of the barbs.

Couillard took his main rival to task over comments she made Wednesday about him and accused fraudster Arthur Porter.

Through an intermediary, Porter voiced his support for the Liberal leader from a Panamanian jail cell where he is awaiting a decision on extradition to Canada on fraud charges. In brief interview posted online, Porter said he still considers Couillard a friend.

Asked about Porter's comments, Marois described the two men as "birds of a feather."

Couillard, who has been fending off campaign attacks for his past dealings with Porter, clearly has had enough with the attacks.

"It's such a mediocre way to talk about someone else," he said as he campaigned in Sherbrooke ahead of a blitz of several towns later in the day.

"Quebecers judge people. When you are on a 33-day campaign, you're always in front of people when you use that tone, when you use those words, in my opinion, you send a really negative impression to people."

Porter is a former hospital administrator who is facing fraud charges in Canada stemming from the awarding of the McGill University superhospital contract. He has denied any wrongdoing.

Porter first struck up a friendship with Couillard when the latter served as health minister in Jean Charest's Liberal government.

The two set up a company together in 2010, but the Liberal leader has said no business was ever conducted and that there were no financial statements before the firm dissolved in 2012.

During the campaign, Couillard released official documents about the dealings to try to stem the attacks.

He said Thursday the message being sent by Marois and the PQ is they are "ready to try anything, including insults, disparaging remarks and guilt by association."

"It would be so easy for me to reply in the same tone, but I will not do it," he said.

It hasn't been easy, Couillard admitted. He said he has had to bite his tongue during the acrimonious campaign, which reached the 30-day mark on Thursday.

"I think I built with patience, and sometimes with a certain degree of pain, to answer insult, not by insult, but by respect, keeping a respectful tone," Couillard told reporters.

"This gives me, I believe, the credibility the day after the election to rally Quebecers."

Couillard said Quebecers don't want to end up back at the polls in another 18 months in the event of a second consecutive minority government.

"Let's give an election holiday for four years to Quebecers," he said.

"I think we need a majority government. And we need a Liberal majority because we need a government that's going to be focused on employment, the economy, better education and better health care."

Marois had no events on Thursday morning and was to give a speech to the Montreal Board of Trade later before heading north of Montreal.

Coalition Leader Francois Legault warned, meanwhile, that the election of a Liberal government would be a serious blow to Quebec's finances and could lead to a drop in the province's credit rating.