Calgary, Edmonton could show cracks in Conservatives' fortress Alberta

This is the fifth in a series that will run until the end of the campaign, taking an in-depth look at where the polls stand in every region of the country and which seats are up for grabs. Check out the last instalment, where the spotlight was on northern and eastern Ontario.

Alberta is likely to stay a deep hue of blue on election night, but the provincial map could also be speckled with a few flecks of red and orange. And that alone is big news in a province that has been dominated by the Conservatives for decades.

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In 2011, all but one seat in Alberta was won by the Conservatives. The party captured 66.8 per cent of the popular vote in the province, with the New Democrats (who took that one seat) trailing at a distance with 16.8 per cent. The Liberals captured 9.3 per cent of the vote and the Greens 5.3 per cent.

That outcome followed a long series of elections in which non-conservative parties have struggled in Alberta: they have not won more than two seats in any election since 1993 (when Jean Chrétien's Liberals took just four).

That could change radically this election. While the Conservatives are still favoured to win a big number of seats, as many as a dozen ridings in Alberta could be at play.

The Conservatives still hold a robust lead in the province in the CBC Poll Tracker, with 53.4 per cent support, followed by the Liberals at 22.2 per cent and the New Democrats at 19.3 per cent. This marks a change from where the polls stood earlier in the year. Before the election was called, the Tories were more routinely polling under 50 per cent in the province.

There has been more significant movement between the two opposition parties. The NDP had been solidly in second place in Alberta for much of the year, polling between 27 and 29 per cent support in the three months preceding the election call. But five of the last seven polls with breakdowns for Alberta show the NDP at 20 per cent or less. In the previous 30 polls conducted in Alberta since the campaign began, the NDP scored under 20 per cent only three times.

The numbers have improved for the Liberals, who have polled at or above 20 per cent in six of the last seven polls. They managed that only nine times in the previous 30 surveys. This puts them back in the range of support they were managing in the two years prior to Rachel Notley's surprising victory for the provincial NDP in Alberta's May election.

But Justin Trudeau remains the most unpopular leader in the province, with a disapproval rating averaging 50 per cent in polls conducted during the campaign. His approval rating stands at 36 per cent on average, which ties him with Tom Mulcair. The NDP leader's disapproval rating, however, is five points lower than Trudeau's. Conservative Leader Stephen Harper boasts an approval rating of 46 per cent in the province, but his disapproval rating is also that high.

The projections currently award the Conservatives between 28 and 31 seats in the province, with the Liberals winning between one and four and the NDP taking two. But there are a lot of other seats at play, and enough time left in the campaign to swing the results in seats not currently estimated to be on the fence.

The Conservatives are clearly playing defence in Alberta, but they do have the opportunity to make some numerical gains. Six new seats have been added to the electoral map in the province, and the Conservatives have a good chance of taking all of them. Picking up Conservative-turned-Independent MP Brent Rathgeber's riding is also looking likely, though riding-level polling suggests Rathgeber is competitive.

The following is a list of ridings that each of the parties could pick up on election night. Favourable gains are those in which there is a good chance of the party winning, potential gains are those in which the results may be close and marginal gains are seats in which the party has an outside chance.

Favourable Conservative gains:

• St. Albert-Edmonton.
• Three new seats created in and around Edmonton.
• Two new seats created in Calgary.
• One new seat created in northern Alberta.

But the Conservatives have different opponents in different parts of Alberta: the Liberals in Calgary and the New Democrats in Edmonton.

The Liberals' best chances are in Calgary, where the party narrowly took more of the vote than the NDP did in 2011. They also have a few former provincial members of the legislature running for office in the city.

Potential Liberal gains:

• Calgary Centre.
• Calgary Confederation.
• Calgary Skyview.
• Edmonton Centre.

Marginal Liberal gains:

• Calgary Forest Lawn.
• Calgary Signal Hill.

For the New Democrats, their focus is primarily on Edmonton, where they took just under a third of the vote in 2011. The provincial NDP won a solid majority of the vote in the city and all of its ridings in this spring's election.

Favourable NDP gain:

• Edmonton Griesbach.

Marginal NDP gains:

• Edmonton Centre.
• Edmonton Manning.
• Edmonton Riverbend.
• Lethbridge.

Alberta has never had much of a role in deciding a federal election's outcome, apart from running up the numbers for the Conservatives. But with the potential for a close result on election night significant, three or four seats (let alone a dozen) could prove decisive. For the first time in ages, Alberta is a province to watch on election night.

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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.