Tonight's TVA debate could shake up the electoral map in Quebec

In a few hours, four federal leaders will participate in what could be a watershed event in the current election campaign in one of the country's most volatile battlegrounds Quebec.

The French-language debate organized by the TVA network will feature Liberal Leader Justin Trudeau, Conservative Leader Andrew Scheer, NDP Leader Jagmeet Singh and Yves-Franois Blanchet of the Bloc Qubcois.

It's likely to have a big audience. Ratings for TVA's debate beat by a significant margin ratings for the other French-language debate staged during the 2015 federal election campaign by a consortium of media outlets. And unlike next week's French-language debate, being organized by the leaders' debate commission, the TVA tilt will be unabashedly Quebec-focused.

So this debate could be the event that finally breaks the deadlockin the polls. Even if its English-speaking audience is limited to Ottawa reporters in the parliamentary press gallery, what happens in thisdebate still could have an impact on what happens in the rest of the country. Recall that inthe 2011 election, it was the NDP's surge in Quebec that helped boost the party's fortunes elsewhere in Canada.

On the face of it, the Liberals appear to have a wide advantage in Quebec. The party leads in the province, with just over 34 per cent support in the CBC's Poll Tracker, an aggregation of all publicly available polling data. The Bloc trails in second place with 22 per cent, followed closely by the Conservatives at 21 per cent.

The New Democrats are polling at 11 per cent in Quebec. That puts them just ahead of the Greens, who are running in fifth place at nine per cent.

Green Leader Elizabeth May and People's Party LeaderMaxime Bernier were not invited to participate in the TVA debate.

Liberals, Bloc fighting for seats

Though the two parties don't share a lot of the same voters, the Liberals and Bloc are fighting over a lot of the same seats. Many of those seats are on the fence right now.

The Poll Tracker estimates the Liberals are leading in 45 seats in Quebec. But nine of those are very tight races, while another six look competitive. As many as 15 seats in Quebec could be put at risk for the Liberals if Trudeau turns in a poor performance tonight.

On the flip side, the Liberals are projected to be trailing in five close ridings and competitive in another eight so a strong performance by Trudeau could move as many as 13 seats into the Liberal column. That alone would put the Liberals on the cusp of a majority government.

But there's a lot at stake for Blanchet as well. The Bloc is the only party experiencing what could be charitably called momentum in this campaign. The party has picked up about three percentage points in Quebec since the campaign began. No other party has seen its support move by an average of more than a point in the province.

The Bloc is projected to be leading in 19 seats nearly double the 10 it won in the last election. But more than half of those are considered competitive races, soBlanchethas a lot to lose tonight. He also has a lot to gain, as the Bloc is projected to be trailing in 17 close races. That's a wide range for the Bloc.

A lot of the closest races are Liberal-Bloc contests in and around Montreal, particularly the suburbs to the south and east of the city. Recent polls by Lger and Nanos Research give the Liberals a wide advantage in the Greater Montreal region, with about 40 per cent to 21 or 22 per cent for the Bloc but what matters here is where that support is concentrated. The West Island of Montreal is to the Liberals what Alberta is to the Conservatives a place where the party runs up huge numbers without winning any extra seats.

The Bloc's opportunity lies in the unpredictability of a lot of the races in Quebec. Lger shows a three-way tie between the Liberals, Conservatives and Bloc among francophone voters. A few points in one direction or the other could change the outcome in a lot of seats across the non-urbanregions of the province.

Scheer, Singh playing smaller ball

While the stakes are high for Scheer and Singh as well, there are fewer seats at play for the Conservatives and NDP.

Conservative support is concentrated in just a few parts of Quebec. In a recent survey, Lger found the Conservatives holding a 21 point lead over the Liberals in the Quebec City region. The Poll Tracker puts the Conservatives ahead in 13 seats across the province; only four of those are considered competitive races, while the Conservatives are trailing in another six seats considered winnable for the party.

Those are still important seats for the Conservatives. Considering polling trends in the rest of the country, it's hard to imagine the Conservatives forming a majority government without 15 to 20 seats in Quebec.

For Singh, this debate might be his last opportunity to save the furniture. The NDP has shed a lot of support since the last election. In the ridings that were considered themost hotly contested in Quebec in 2015, the Angus Reid Institute finds the NDP is down 18 points. Those votes have been lost in roughly equal sharesto the Liberals, Bloc and Greens.

The Poll Tracker does not put the NDP ahead in any ridings in Quebec and suggests it is only competitive in one. But it would not take much to give the NDP some hope and May's absence does present Singh with an opportunity.

Lger finds that 30 per cent of Green supporters in Quebec list the NDP as their second choice. The Liberals were not far behind at 25 per cent, but it's clear that a strong performance by Singh particularly on environmental issues could pay dividends without May there to put forward her party's perspective.

If the NDP is able to shave five points off the Greens in Quebec, the Poll Tracker would put the New Democrats ahead in two ridings and competitive in as many as seven. That's a decent amount of furniture saved from the flames.

Maybe the debate doesn't end up moving voters in any significant way (nothing has so far). But in a province that has awarded different parties the most seats in each of the last three provincial and federal elections, the TVA debate provides the best opportunity to dateto shake up this campaign.