The summer months have not shifted the dial dramatically in the voting intentions of Canadians, but the provincial election in Quebec may have put a dent in the New Democrats' support as the party has fallen three points behind the Conservatives in a weighted average of recent federal polls.

With 34 per cent support, Stephen Harper and the Conservatives remain in the lead and have picked up a single point since the last average of federal polls was compiled on Jun. 18. The New Democrats, however, are down four points to 31 per cent support, a drop caused primarily by decreases in Quebec and British Columbia.

The Liberals are up two points since June to 23 per cent while the Greens are unchanged at 5 per cent support.

Story continues below advertisement

The five polls that have been conducted during the month of September have not been in complete agreement, with three of them giving the Tories the edge, one of them pegging the NDP as leading, and another putting the two parties in a tie. But the general trends point to a narrow Conservative lead as parliamentarians get started on a new fall sitting.

With these levels of support, a snap election would likely deliver 142 seats to the Conservatives, an increase of nine over where their polling put them in June but a drop of 21 compared to their current standing in the House of Commons. Thomas Mulcair's New Democrats would win 99 seats, a drop of 24 since June but only one seat fewer than they currently hold. The Liberals would win 59 seats, up 10 since the last projection and 24 more than they now occupy, while the Bloc Québécois would win seven seats and the Greens one.

But the electoral map will change between now and 2015, when the next election is scheduled to be held. With these numbers, and based on the proposed changes to electoral boundaries, the Conservatives would likely win 152 seats, with the NDP taking 107, the Liberals 66, the Bloc Québécois 12, and the Greens one.

In both cases, the Conservatives would not win a majority of the seats in the House of Commons, while the New Democrats and Liberals would, together, command a little more than half.

But that is a far cry from where the New Democrats were only a few months ago, when they were leading in national voting intentions and were a few seats short of a plurality.

The most significant shift in support since June occurred in Quebec, with the provincial election standing out as the most likely cause of the change. After being stuck on the sidelines without a provincial proxy and purposefully staying out of the campaign, the New Democrats have slipped 11 points in Quebec to 33 per cent support. Both the Liberals, up seven points to 23 per cent, and the Bloc Québécois, up four points to 25 per cent, have benefited from the NDP slip. Some polls have even put the Bloc closer to the 32 per cent that their provincial counterpart, the Parti Québécois, took in the Sept. 4 vote.

Whether this increase for both the Liberals and the Bloc is a mere side-effect of the provincial race will be shown in the coming months, when more focus returns to the federal scene. But with the PQ in a minority situation in Quebec City, provincial politics will likely continue to draw the vast majority of Quebeckers' attention, making it more difficult for the NDP to regain support.

Story continues below advertisement

The New Democrats have also suffered a drop in British Columbia, where the party is down six points to 34 per cent. The Conservatives have picked up five points to lead with 38 per cent, a significant change of fortunes. The NDP had led in most polls taken in the province in recent months, but in only one of the five surveys done in September.

Voting intentions in Ontario have remained relatively stable, with the Conservative up one point to 37 per cent, the NDP down two points to 30 per cent, and the Liberals up one to 27 per cent. Elsewhere, the Tories hold significant leads in Alberta (58 per cent to the NDP's 21 per cent) and the Prairies (46 to 33 per cent), while the NDP is well ahead in Atlantic Canada with 38 per cent to 30 per cent for the Conservatives.

If the NDP's numbers return to where they were in Quebec before the provincial race took place they will move into a tie with the Tories. Overall, the contest between the two parties has not changed much over the last few months. The next few months, with the start of the Liberal leadership race and at least three by-elections, will likely see more variation in support.

ThreeHundredEight.com's projection model aggregates all publicly released polls, weighing them by sample size, date, and the polling firm's accuracy record. The seat projection model makes individual projections for all 308 ridings in the country, based on the provincial and regional shifts in support since the 2011 election and including the application of factors unique to each riding, such as the effects of incumbency. Projections are subject to the margins of error of the opinion polls included in the model, as well as the unpredictable nature of politics at the riding level.

Éric Grenier writes about politics and polls at ThreeHundredEight.com .