John Tory was taking a big risk when he ran for Toronto mayor in 2014. He had lost once before. He had struck out as leader of the provincial Conservatives. If he lost again, it would be the end of his political ambitions.

To win voters over, he put a big shiny promise in the store window. SmartTrack would "solve congestion" in Toronto by making use of existing GO Train tracks to carry commuters around on a "surface subway." It would be completed in seven years – fast for a transit project – and it would be paid for "without new taxes."

This last promise was crucial. One of Mr. Tory's competitors in the election campaign was Mayor Rob Ford, still a potent political force despite the crack scandal. Mr. Ford, of course, had built his career posing as a champion of the taxpayer. If Mr. Tory had told voters that the costly SmartTrack project was going to hit them in the wallet, Mr. Ford would surely have used the admission as a club to beat him with.

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Two years later, a report on financing SmartTrack has just come out at city hall. It was approved on Tuesday by city council's executive committee. The report says that after provincial and federal contributions, Toronto could be on the hook for about $2-billion – no small change. Where will all the money come from? Back in 2014, Mr. Tory said he would raise it through the alchemy of Tax Increment Financing (TIF), which takes tax revenue from development to pay for infrastructure.

The financing report from city staff suggests that TIF alone won't do the trick. It recommends looking at ordinary development charges, sales of city assets and, yes, property-tax increases as well.

Mr. Tory insists the report doesn't mean the city will need to raise property taxes to pay for SmartTrack. It could choose some of the other options in the report. He points out that city council is soon to get another report on possible new taxes and fees that it could tap, too. Yes, but if it uses money from those sources for SmartTrack, the cash won't be available for other pressing city needs.

After a meeting with Ontario Premier Kathleen Wynne on Tuesday, the mayor admitted that the SmartTrack plan has changed since he first rolled it out, but said his critics are "just busy criticizing." Most Torontonians, he said, just want to get on with building transit.

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It is true that the city is impatient for action after years of slow progress on building out the mass transit network. Perhaps voters will be willing to fork over the higher taxes that, one way or another, now seem inevitable to pay for it. But didn't Mr. Tory suggest that SmartTrack would come at no extra cost to the taxpayer? To be charitable with terminology, that was misleading. Even if he believed it to be true – and many questioned it at the time – it was a rash commitment.

Most politicians are not dishonest by nature. They are decent people who wouldn't dream of being less than straight with their friends or neighbours. But in their business, telling the truth is dangerous. That is especially true when the subject of taxation is involved.

If they level with the public and admit they will need to raise taxes to pay for everything they are promising, their opponents will jump all over them. Voters may throw them out of office, or keep them from getting there in the first place. That means they will not be able to do all the great things they are planning, things that they sincerely believe will help the people they hope to represent.

Is it really necessary to be blunt, they may ask themselves? Wouldn't it just give more ammunition to their hostile rivals? What harm would it do, really, to fudge the facts a little, to paint a picture for voters in hopeful pastel shades instead of stark black and white? With the best of motives, they rationalize misleading the public.

Every time politicians try to pull the wool over the eyes of voters, cynicism about politics grows. That cynicism makes it harder for governments to get things done, because people don't believe what their leaders say and won't rally behind them. As your auntie used to say, honesty is the best policy.