Alberta has been a conservative fortress for decades. Successive conservative parties (Progressive Conservatives, Reform, Canadian Alliance, and the Conservative Party of Canada) have dominated the federal scene.

If you need proof, have consider these facts:

In the 2011 election, 27 out of 28 elected MPs were Conservative (Linda Duncan, Edmonton-Strathcona NDP was the sole exception) and their share of the popular vote was an astounding 66.8 per cent;

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Between 1968 and 2011, there were 15 elections and the conservative parties won 319 of the 336 individual riding contests in Alberta;

No Liberal or New Democrat MP has been elected in Calgary or rural Alberta since 1968.

But the fortress may have a few cracks heading into the Oct. 19 election. Not surprisingly, this is why all three major party leaders were in Calgary for Stampede events. Stephen Harper, Thomas Mulcair and Justin Trudeau did not just wear cowboy hats and flip pancakes, they spoke at partisan political rallies that were well-attended by party faithful.

Mr. Mulcair and Mr. Trudeau are targeting Alberta because they see potential for a breakthrough.

They have some reasons to be optimistic.

First, poll numbers for both Liberals and NDP have been rising in Alberta. The latest aggregate numbers show the NDP at 30 per cent and Liberals at 19 per cent. But in rural Alberta, support for the Liberals and NDP is likely in single digits; so this means their support in key Edmonton and Calgary constituencies is higher than the published poll numbers.

Second, both parties have already recruited a few star candidates. For example, the Liberals have popular former Liberal MLAs Kent Hehr (Calgary-Centre) and Darshan Kang (Calgary-McCall) running in federal constituencies that overlap their former provincial ones. In Edmonton, the NDP has recruited Alberta Federation of Labour president Gil McGowan to run in Edmonton-Centre.

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Third, the sustained popularity of progressive mayors Naheed Nenshi in Calgary and Don Iveson in Edmonton offers hope for the Liberals and NDP.

Fourth, the New Democrats, but also the Liberals, were buoyed by the surprise victory of Rachel Notley in May: If the provincial NDP can break the 44-year PC dynasty, they feel that they have a chance federally.

Their optimism must be tempered. While the walls may have cracks, the fortress is not on the verge of collapse. Support for the Liberals and NDP is still non-existent in rural Alberta. Even within Calgary and Edmonton, the parties are targeting selected ridings (most of them in the downtown core). The Prime Minister might have challenges in other parts of Canada, but he remains popular with Albertans, and he is surrounded by many strong MPs. With the new riding boundaries, the province now has 34 seats (about 10 per cent of the country's total) and the Conservatives will still win, at the very least, 28 to 30 of them.

But the impact of winning a few seats in Edmonton or even one in Calgary would carry more weight for the other two parties than their raw numbers merit. Just the idea of a potential breakthrough has allowed Mr. Mulcair and Mr. Trudeau to say in other parts of Canada that if the NDP and Liberals can win seats in Alberta, they can do it anywhere.

It also means Mr. Mulcair and Mr. Trudeau will actually be seen in Alberta during the election campaign. In 2000, Jean Chrétien avoided Calgary completely, and in 2004, Paul Martin spoke only at a hotel near the Calgary airport. Meanwhile, the Conservatives would actually have to allocate resources to campaigning in Alberta. Both Joan Crockatt and Devinder Shory (who are being challenged by Mr. Hehr and Mr. Kang) are already campaigning hard. This federal focus would also ensure Alberta cabinet representation, no matter which party forms government in the fall.

Finally, with the election expected to be very tight, the Conservatives cannot afford to lose any seats. Even just three or four would be a major breach in the fortress.