The Rob Ford scandal is not just a sad story about a troubled man. It is more than a titillating diversion or an attention-grabbing headline. Its effects go beyond causing acute embarrassment for Toronto. It poses a threat to the success of Canada's biggest city.

Toronto stands at a turning point in its 180-year history. It is growing as never before, taking in hundreds of thousands of people from every corner of the globe. Its downtown is becoming a little Manhattan, sprouting scores of new office and residential towers. Its cultural scene is a marvel, drawing crowds to its film, art and music festivals.

But its governance is a mess. City council was ineffectual long before Mr. Ford came along with his promise to "stop the gravy train." He rode to office on a vow to bring a new rigour to city government, with better service for residents and more respect for taxpayers.

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At first, he made some progress, killing an unpopular tax, trimming the budget and contracting out some services. Now his mayoralty is imploding.

No less that the chief of police has confirmed that authorities have a copy of a video that allegedly shows him smoking crack cocaine. So much for his assertion that such a video does not exist. His credibility has been demolished. He can no longer claim he is the innocent victim of a conspiracy by "lefties" and media "maggots" to sully his name.

If the video were not enough, the police have compiled a staggering trove of information showing the mayor consorting with a cast of shady characters. Among them is Alessandro Lisi, a man who stands accused of drug offences and, now, extortion.

It is hard to see how Mr. Ford can explain his way out of this even if he tried. How does he explain the suspicious packages Mr. Lisi left for him in his car?

Thursday's disclosures rip the veil from a shadow life that the mayor appears to have been living – a life not remotely consistent with his role as the city's chief magistrate. He was elected to be a leader, someone to set an example for the city. Instead, he has become an example of how not to act.

The irony is that the man who vowed to bring discipline to city hall has been undone by his lack of self-control. Even though the mayor does not face criminal charges – and the allegations against him have not been proven in court – there is a stain on his office that cannot be removed except by his speedy departure.

If, a few months ago, he had admitted there was some substance to the mounting allegations about his behaviour, it would have been one thing. If he had said he had a problem and was seeking help, the city might have been forgiving.

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Instead, he has steadfastly refused to comment, lashing out at his critics at every opportunity and accusing them of drawing attention away from his accomplishments. But it is he who has become the distraction. The city deserves better.

Chief Bill Blair spoke for many when he said that, as a citizen, he was disappointed. He called it a "traumatic issue" for Torontonians and "the reputation of this city, and that concerns me."

But the Ford scandal goes beyond the threat to Toronto's good name. It comes at a time when it desperately needs confident, intelligent leadership. If it drags on, the city could find itself tied in knots at a time when it is struggling with serious problems that could stall its recent progress – problems that range from the crumbling Gardiner Expressway downtown to an under-built, run-down transit system to a public housing system that needs hundreds of millions of dollars in repairs.

The city has already been damaged by Mr. Ford's inept leadership on the transit file, causing years of delays and millions in waste as the city flipped and flopped from one transit plan to another. Imagine if he hangs on for the remaining year to the next election. The noise over this shabby business, raised to an almighty din with Thursday's revelations, will drown out everything he tries to do. His mayoralty, already adrift, has been crippled beyond recovery.

It is time for him to go. After all the evasions, all the nonsense, all the denials, this should be the end of the road for Mr. Ford. For his own sake and the sake of the city, he should resign as soon as possible and let Toronto get on with building its future.