The polls go up, the polls go down. What has remained constant is the close contest between all three parties, with the New Democrats leading most of the time, the Conservatives usually second, and the Liberals in third. But the polls also suggest that some potentially more enduring trends are unfolding at the regional level.

The latest poll added to the CBC Poll Tracker, an Abacus Data survey published Tuesday and placing the NDP in the lead nationally with 35 per cent, followed by the Conservatives at 29 per cent and the Liberals at 26 per cent, has widened the advantage the New Democrats have over the other parties.

The NDP leads with 33.5 per cent support in the averages, with the Conservatives at 29.4 per cent and the Liberals at 26.7 per cent. The Greens are averaging 5.8 per cent support, while the Bloc Québécois has slipped to just 15.5 per cent in Quebec.

The trend lines drawn out by these averages since the beginning of the campaign represent a wobbling back-and-forth for each of the parties.

Listen to the podcast

This week, Eric Grenier speaks with David Colletto, CEO of Abacus Data, about his new poll that suggests 70 per cent of voters have not yet fully decided who they will vote for on Oct. 19.

Listen to the podcast below and download other episodes or subsribe here.

The polls have been quite consistent for both the Conservatives and the Liberals. The Tories have ranged between 27 and 32 per cent since the start of the campaign, and in two-thirds of those polls the Conservatives have registered at least 29 per cent support. The Liberals, meanwhile, have been between 26 and 29 per cent in seven of the last nine polls.

But the New Democrats have been all over the map. With a range of between 29 and 39 per cent since the beginning of the campaign, and with no discernible trend, the NDP appears to be most at mercy of sampling error and, perhaps, fleeting movement to another party. Even if the highest and lowest outliers are dropped from their ranges, they have still been pegged at anywhere between 30 and 35 per cent support, enough to put them narrowly in second place or comfortably in first.

That means that if an election were held today, the party could easily find itself at either extreme of the NDP's projected likely seat range: 113 to 142 seats. This effectively puts them in a tie with the Conservatives, who range between a projected 106 and 147 seats. The Liberals, at between 69 and 98 seats, are solidly back in third place after flirting with the Conservatives' low range of seats.

Regions to watch

One province that helped spur the NDP's rise into first place in the polls nationwide is worth keeping an eye on. Some surveys are hinting at a softness in the NDP's numbers in Alberta, with four of the last five polls in the province putting the party between 19 and 23 per cent. That compares poorly to the 28 to 34 per cent the NDP was polling at in the previous five surveys from Alberta. Three pollsters have the party down from their pre-writ polling, though others do not.

Overall in Alberta, the New Democrats have dropped to 21.6 per cent in polls conducted up to Aug. 17 from 29 per cent in the average on Aug. 10. The Conservatives have taken advantage, rising to 56 per cent from 49.5 per cent. The projection now gives the Tories between 29 and 32 seats in Alberta, up from 24 to 29 a week previously. The NDP has gone from a range of three to seven seats down to just two to three.

Another region with some noteworthy trends is Atlantic Canada. Both the Liberals and New Democrats are trending positively, with the Liberals scoring 41 per cent or more in five consecutive surveys and the NDP 36 per cent or more in three straight polls. The Conservatives, meanwhile, have registered 18 per cent support or less in those three surveys.

On average, that puts the Liberals at 43.9 per cent, up more than five points since the end of July. The NDP is up almost four points to 34.7 per cent, while the Conservatives have shed over six points' worth of support, falling to just 18.6 per cent. The Conservatives are now projected to win just one to five seats, compared to a range of six to 10 seats on July 28.

Ontario remains a close race, with all but one recent poll putting the support of the three main parties within each poll's respective margin of error. And while the numbers in the Prairie provinces look steady, a recent big-sample sounding by Insightrix Research in Saskatchewan put all three parties in a close race in Regina (though how much of the Liberals' support is concentrated in Ralph Goodale's riding is an open question), while the New Democrats and Conservatives were running neck-and-neck in the rest of the province.

Though Abacus does suggest that the NDP could be breaking from the pack, the consensus view is that the three parties remain in a virtual deadlock. But regional trends could shift the balance in dramatic ways, even if the national numbers continue to show little change.

CBC's Poll Tracker aggregates all publicly released polls, weighing them by sample size, date and the polling firm's accuracy record. Upper and lower ranges are based on how polls have performed in other recent elections. The seat projection model makes individual projections for all ridings in the country, based on regional shifts in support since the 2011 election and taking into account other factors such as incumbency. The 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. The polls included in the model vary in size, date and method, and have not been individually verified by the CBC. You can read the full methodology here.

The questions asked in the polls mentioned in this article were as follows:

Abacus: "If a federal election was held tomorrow, which one of the following parties would you vote for in your constituency?"

Insightrix: "As you may be aware, a general Federal Election has been called on October 19th, 2015. Are you planning on voting in this election? Which of the following parties are you planning on voting for?"