MONTREAL - A revamped format and the appearance of the first woman party chief in a Quebec election debate will be among the new wrinkles when voters tune in to see Jean Charest, Mario Dumont and Pauline Marois square off Tuesday night.

The debate is potentially pivotal in what has so far been a ho-hum election campaign.

Marois has been getting ready for the last few days, and the Parti Quebecois leader took a brief break on Monday to accuse the Liberals of overestimating investments in their recent financial update to the tune of $11 billion.

Finance Minister Monique Jerome-Forget later stood by the numbers.

Marois and Dumont will be hoping the debate gives them an opportunity for their parties to start gaining ground on the Liberals.

A poll of 3,070 Quebecers released Monday pegged Liberal support at 46 per cent, compared with 34 per cent for the PQ and just 12 per cent for Dumont's Action democratique du Quebec.

Those numbers would have placed the Liberals in a clear position to seal a majority government.

The Leger Marketing survey, which was conducted Nov. 18-23, has a margin of error of 1.8 percentage points, 19 times out of 20.

Marois looked serene and joked as she allowed cameras to grab images of her sitting down with debate advisers.

"I will try to explain my projects to Quebecers, I will talk about my ideas for the family, for education, for health and the economy," she said. "That is my goal in this debate."

Charest commented on the debate during an appearance on Sunday, saying he didn't like the level of personal attacks so far in the campaign.

Observers say the Liberal leader was trying to lower expectations for the showdown and that Marois' presence may keep things civil.

"I think it will change the tone," said political analyst Jean Lapierre. "You cannot be bullish or impolite in front of a woman, otherwise you look stupid.

"I think this is going to be a much more civilized debate because of the presence of a woman because you don't have to show that much testosterone."

Denis Moniere, a political science professor at the Universite de Montreal, said Quebecers aren't impressed by attacks and would likely be even less so with aggressive outbursts against Marois.

"However, I think it will be ferocious between Mr. Charest and Mr. Dumont."

The two-hour French debate will feature opening statements and four debate segments of 22 minutes. Each will start with a question from a voter and there will also be three one-on-one encounters of three minutes each.

Those were some of the conditions laid down by Charest to get his participation. Organizers originally wanted to copy the federal leaders' debate, which had party chiefs sitting around a table.

But observers also noted that format allowed opposition party leaders to gang up on Prime Minister Stephen Harper, something Charest likely wanted to avoid despite his prowess as a feisty debater.

"Mr. Charest doesn't really have to make gains in this debate," said Moniere, referring to the Liberals' consistent strong showing in opinion polls. "His objective is to keep his support.

"But for the other two, they have to absolutely make a breakthrough."

That probably still wouldn't come at the expense of the Liberals, he said, because their supporters are unlikely to budge.

While this will be Marois' first outing in such a debate, Charest and Dumont have been here before.

Charest had his first debate as Conservative leader in 1997 and was widely thought to have put in a strong performance.

His 1998 debut as Liberal leader saw him eclipsed by then-PQ leader Lucien Bouchard but he bounced back with a convincing show in 2003 before appearing lifeless in last year's event.

Dumont has participated in four leaders' debates.

When he's on his game, Charest can be engaging, wily and funny.

"When he turns it on, he really is the master of his domain," said Antonia Maioni, director of the McGill Institute for the Study of Canada. "But when he doesn't, there's a problem."

Moniere agreed, calling Charest "an excellent debater."

"This is not the case for Madame Marois. I think the leader with the most difficulty, who has the biggest challenge, is Madame Marois because she has not yet demonstrated that she has the ability to rally a large number of voters."

Lapierre was blunt about Dumont, who goes into the debate on the heels of an eyebrow-raising decision to don a blond mullet wig and appear in a comedy skit on French-language television. He also recently surprised some by apologizing for his poor performance as Opposition leader.

"For Mr. Dumont, it's do or die," Lapierre said. "Either he makes a big coup or he's back into oblivion."

That could be a real challenge for the ADQ leader, Moniere said.

"The problem for Mr. Dumont is that people have already made up their mind about him," he said. "He lacked seriousness in the last few months and this has hurt his credibility. It's very hard to get past that."