Incumbent mayoral candidate Naheed Nenshi trails challenger Bill Smith by 17 points in the latest poll from Mainstreet Research.

"Nenshi's path to victory on Oct. 16 is growing thinner," Mainstreet president Quito Maggi said in a release.

"With time running short, the former world's greatest mayor faces a growing deficit that will be hard to overcome."

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He added that the poll results suggest "the near certain election of Bill Smith" and "may signal a seismic shift in Calgary civic politics."

"What the effect may be on down ballot candidates is impossible to say from this data, but it's likely Nenshi will not be the only incumbent to be the victim of this change election," Maggi said.

Survey respondents were asked: "If the election for Mayor of Calgary were held today, which candidate would you support?"

The results were:

Bill Smith — 48 per cent

Naheed Nenshi — 31 per cent

Undecided — 13 per cent

Andre Chabot — 6 per cent

Someone else — 3 per cent

The poll was commissioned by Postmedia, the company that owns the Calgary Herald and Calgary Sun, and conducted over a period of two days, Oct. 3-4.

"As the certainty of a Bill Smith election becomes clearer, the risks increase again on the front-runner, and any late mistakes could reverse the gains of the past week," Maggi said.

"But while Calgarians begin to vote in advance polls, the Smith campaign continues to peak."

"It's important to remember that candidates can outperform their polling numbers," Maggi added.

"Strong get-out-the-vote campaigns can make a difference — but there's only so much those campaigns can accomplish. In tight races they can make a difference but this is looking less competitive by the week."

In a statement, Nenshi's campaign team said they are not worried about the numbers.

"We have great confidence in our internal numbers. We'll leave it up to the media to question the validity of the polls. We strongly believe that Calgarians will vote to move forward... not backwards," said Chima Chima Nkemdirim, the chairman of the Naheed Nenshi Re-election Campaign.

Mainstreet surveyed 1,500 Calgarians using using automated, interactive voice-response (IVR) technology and responses were weighted using demographic and geographic information to targets based on the 2016 Census.

For comparison purposes only, a random sample of this size would yield a margin of error of plus or minus 2.5 percentage points, 19 times out of 20.