John Tory has opened up a 22-point lead in the race to be Toronto mayor, with last-minute addition Doug Ford holding onto his brother's support and Olivia Chow in third, new polling numbers show.

The fine print of the poll holds little hope for Ford Nation however. Support for Doug Ford, who entered the contest in place of his ailing brother Rob Ford, appears to have little room to grow, the poll suggests.

Mr. Tory has the support of almost half of decided voters if the election were held today – 49 per cent – followed by Mr. Ford at 27 per cent and Olivia Chow at 24 per cent, says a Nanos Research poll of 1,000 Torontonians conducted last week for The Globe and Mail and CTV News.

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A similar poll done in late August before Rob Ford and David Soknacki left the race gave Mr. Tory a 14-point lead with support from 42 per cent of decided voters. Rob Ford was at 28 per cent and Olivia Chow at 26 per cent.

The poll comes as Doug Ford jumps into the race in earnest, going head to head in a debate for the first time against his two main rivals Tuesday night.

Do you have a positive, somewhat positive, somewhat negative or negative impression of Doug Ford Region Responses Positive Somewhat positive Somewhat negative Negative Unsure Canada 2014-09 1000 19 11.5 10.9 51.4 7.2 Etobicoke 136 25.7 8.8 13.2 47.8 4.4 North York 273 21.2 11 11.4 48 8.4 Scarborough 243 23 18.1 10.3 39.1 9.5 Old Toronto 348 11.8 8.3 10.1 64.1 5.7 Males 500 20.6 11.4 10.4 49.6 8 Females 500 17.4 11.6 11.4 53.2 6.4 18 to 29 125 22.7 11.7 15.6 45.3 4.7 30 to 39 131 18.3 9.9 16 50.4 5.3 40 to 49 172 17.4 16.3 11.6 49.4 5.2 50 to 59 255 18 12.9 7.5 54.9 6.7 60 plus 314 19.4 8.3 9.2 52.5 10.5

There was speculation that the late substitution by the Ford brothers – with Rob Ford withdrawing from the race to undergo treatment for a rare and aggressive form of cancer – would cause a major shift in the campaign. So far, the numbers show the switch did not put a dent in the support of Ford Nation.

Doug Ford, who entered the race less than an hour before the deadline to get on the Oct. 27 ballot, has a loyal group of backers, with 81 per cent indicating their support is firm, a number pollster Nik Nanos says is unusually high.

"It means that there are people committed to the Ford Nation and Rob Ford and Doug Ford are interchangeable to them, without any negative fallout," he said.

But with just 31 per cent of respondents saying they have a positive or somewhat positive impression of the older Ford brother, it will be difficult to increase that base, Mr. Nanos predicted.

"There is not a lot of room for growth for the Fords," he said. "The Ford Nation is in a very difficult spot. There are high negative impressions of both brothers. "Even after his hospitalization, the poll found 54 per cent of respondents had a negative impression of the mayor and 51 per cent had a negative impression of his brother.

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That compares with positive impression ratings for Mr. Tory and Ms. Chow, suggesting any support either would lose would go to the other, rather than the Ford camp.

Transit and gridlock continue to dominate the campaign, with even more respondents identifying it as the top issue than last month.

"For all intents and purposes, this is a one-issue campaign. It's about transit and gridlock full stop," Mr. Nanos said.

As a result, Mr. Tory as the front-runner must ensure his transit plans are "bulletproof," he said.

"On the policy front, the only thing that can derail it is some kind of massive blunder or mistake on transit," the pollster predicted. "Beyond that it would be a personal mistake or revelation."

Mr. Tory said in a statement that the new poll will not alter his strategy. "Whatever the numbers are, they don't change the way I campaign – like I am five points behind," he said.

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Ms. Chow responded to the poll numbers by attacking Mr. Tory's transit plan as a "slippery track … that has lots of holes in it," another salvo in an ongoing attempt to undercut the centrepiece of his campaign.

"I think we need a plan that is comprehensive, that is supported by experts," she said Monday evening. "It shouldn't just sound good, it needs to actually work."

Doug Ford's campaign did not reply to a request for comment.

The 11th-hour switch by the Ford brothers did not sit well with poll respondents. About half said they were uncomfortable or somewhat uncomfortable with the change. Those who said they were comfortable with the move were likely to indicate they like the brothers and believe in their policies.

The mayor is running for his former council seat in Ward 2.

Mr. Tory's support is strong in all parts of the city. Doug Ford is leading Ms. Chow in every part of Toronto except the old city, where she has the support of 29 per cent of decided voters. But even here, considered the core area for support for the former city councillor who represented Trinity-Spadina as an NDP MP, Mr. Tory has a commanding lead, with 54 per cent of decided voters – the highest support of any area of the city.

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Mr. Ford's support is strongest in Scarborough, at 35 per cent of decided voters, followed by Etobicoke at 33 per cent. That compares with just 17 per cent in the old city.

With voting day five weeks away, voters are more sure about their intentions, with the number of undecided voters dropping to 8 per cent from 17 per cent in August.

When undecided voters are included in the numbers, Mr. Tory leads with 46 per cent, followed by Mr. Ford with 25 per cent and Ms. Chow with 22 per cent.

The poll, taken between Sept. 16 and 20, sampled residents who said they were "very likely" to cast a ballot in the October election. It has a margin of error of plus or minus 3.1 percentage points, 19 times out of 20.

With reports from Ann Hui and Oliver Moore

Impressions of Candidates

In a random telephone survey of 1,000 very likely Toronto municipal voters between Sept. 16 to 20, respondents were asked: Do you have a positive, somewhat positive, somewhat negative or negative impression of the following individuals (Charts may not add up to 100 due to rounding)

SOURCE: Nanos Research