MONTREAL -- Quebec's quarrelling political leaders have found common ground as they enter the final stretch of the election campaign: they agree this has been the dirtiest of races.

Quebecers will cast their ballots in Monday's vote, a snap election called by Parti Quebecois Leader Pauline Marois last month as her minority government was atop the polls.

At the time, public opinion surveys even suggested a majority mandate was within Marois's grasp, thanks to support for her party's controversial secular charter.

But much appears to have changed in Quebec as the final weekend begins.

Rookie Liberal Leader Philippe Couillard is now the one thought to be within striking distance of a majority government, while support for the PQ has faded, particularly among the always-crucial francophone voters.

The PQ's collapse began after Marois spent a couple of days musing about how an independent Quebec would operate, surprising public reflections that followed the stunning arrival of her star candidate: media baron Pierre Karl Peladeau.

The polarizing majority owner of the Quebecor empire raised eyebrows -- and his fist -- in vowing to make Quebec a country even though most of its citizens oppose secession from Canada.

An electoral defeat on Monday would force the PQ to confront the prospect that its pro-sovereignty dream is politically toxic.

Since that first week of the campaign, the race has descended into a brawl where candidates have attacked the integrity of their rivals amid allegations of backroom deals, dubious business relationships, tax havens and questionable political financing.

Veteran politician Marois has described the campaign atmosphere as the most negative she has ever seen, insisting that just talking about it has caused her "heart to ache."

"It makes me profoundly sad -- very profoundly," Marois told reporters a few days ago.

"We're living in a climate of imaginable suspicion that we've never seen in Quebec."

Couillard has also lamented the mood of the campaign, saying it has been "harsh" since the beginning.

He has maintained he's stayed above the fray, even though he kicked off the campaign by saying he "detested" the outgoing PQ government.

"I would say that to the contrary, people have noticed my measured tone -- I have never responded to mud, with mud," the increasingly confident Couillard told a news conference a few days ago when asked about his own behaviour on the trail.

"There have been literal insults directed at me. I didn't answer them with insults. Why? Because on April 8 I want to govern for all Quebecers."

Francois Legault, leader of the Coalition party, believes the acrimony is rooted in the fact this is only the second election campaign since Quebecers learned about the corruption and collusion linked to their political class.

Legault expects such attacks to continue until a final report is produced from the province's ongoing corruption inquiry, known as the Charbonneau Commission.

"If we no longer had to wait for the Charbonneau Commission's results before having an election, maybe there would be less mudslinging," he said when asked about the negative flavour of the campaign.

"I'm starting to understand why Quebecers are disgusted by everything they see and hear every day in the media."

Along with the integrity issues, other dominant themes have overshadowed everyday voter concerns like the economy, health care and Quebec's crumbling infrastructure.

The parties have all made promises to address these issues, but leaders have faced repeated questions on matters such as Quebec independence.

"It makes me smile a bit when we say that we don't have a campaign on ideas," Couillard said recently.

"Each day we have made a proposal to Quebecers... So, all the party proposals are there."

Couillard, however, led an early offensive against the PQ, warning the party would lead the province to a third sovereignty referendum. His opponents countered by trying to paint him as a fear monger on the subject of independence.

Leading up to the election call, the PQ was expected to campaign on its controversial-yet-popular secular charter, but it has struggled to place the plan front and centre.

The proposal, which polls suggest has the support of most Quebecers, calls for a ban on religious headwear in the public workforce.

Marois has said she is ready to re-introduce the values charter and would even invoke the rarely used notwithstanding clause to ensure it's adopted.

But the charter was sidelined early in the campaign, when Marois fielded questions about sovereignty for days after Peladeau's announcement. The PQ, however, realized that discussing independence hurt its campaign.

Marois tried to regain control of her message, an effort that led her to lightly push Peladeau, one of Canada's most-powerful moguls, away from a news conference microphone when he leaned in to answer a reporter's question.

Over the last month, the electorate has witnessed a flurry of attacks against the integrity of candidates, particularly those running for the PQ and Liberals. Here are some examples:

-- Marois's husband, Claude Blanchet, allegedly solicited $25,000 to fund her PQ leadership bid in 2007, said a report by Radio-Canada. Marois and Blanchet denied the allegation.

-- Couillard had to defend himself after Radio-Canada reported he placed money in an offshore tax haven while practising as a neurosurgeon in Saudi Arabia before his political career. The Liberal leader said there was nothing illegal about the account at the Royal Bank of Canada branch in Jersey, in the Channel Islands between England and France.

-- Peladeau was forced to explain why more than 60 companies that appear linked to Quebecor and its subsidiaries are registered in the state of Delaware, which one political rival said has been qualified as a top tax haven. Peladeau replied by saying he did nothing wrong and there's no advantage to being incorporated in Delaware.

-- Marois had to explain her party's decision to keep quiet about a meeting between two of its senior officials with provincial anti-corruption officials in February.

-- Couillard was criticized by Marois for having incumbents from the party's scandal-plagued Charest era who rejected numerous opposition demands to call the provincial corruption inquiry.

-- Peladeau had to respond to rivals' concerns by insisting his vast media holdings, which would be placed in a blind trust if he's elected, would provide independent coverage.

-- Couillard had to defend a $1.2-million severance package given to Gaetan Barrette, one of his star candidates, prior to his jump into politics. Barrette was president of the federation representing medical specialists until this year.