Roy Norton sounds more like a campaign pitchman than a Canadian diplomat as he works a lunch crowd in suburban Detroit, calling opponents liars and "scoundrels" and urging Michigan voters to defeat a proposal on their state's November ballot.

Canada's chief envoy in Michigan is taking a public role in a political debate that is playing out across the Great Lake State: whether to embrace a new bridge project between Windsor and Detroit that would broaden the most important conduit in Canadian-American trade.

Canadian foreign-service officers don't normally stand at the front of the stage with a U.S. election nearing, but Mr. Norton is under clear orders from Ottawa to counter what Canada describes as a blatant misinformation campaign by those who want to stop the new span.

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Time is running out to set the record straight as Mr. Norton criss-crosses Michigan to speak out in favour of the bridge.

The immediate future of what the Harper government calls Canada's No. 1 infrastructure project is now in Michigan voters' hands. On election day, this Nov. 6, their decision will determine whether the bridge is clear to proceed or whether it becomes tangled in a complicated legal battle.

An American billionaire who owns the only existing bridge between Windsor, Ont., and Detroit has managed to trigger a public vote on the second span even though Prime Minister Stephen Harper and Michigan Governor Rick Snyder inked a deal to build the new crossing this past June.

Interests working for Ambassador Bridge owner Manuel (Matty) Moroun, who insists there is not enough traffic for two spans, have managed to put a question on the November ballot asking voters whether a statewide referendum should be required for any new public bridge to Canada.

The "The People Should Decide" ballot committee for Proposal No. 6, that campaign finance researchers say is largely funded by Moroun interests, has flooded the airwaves with TV ads denouncing the new bridge. Mr. Moroun has spent close to $30-million on the bridge ballot campaign, the Detroit Free Press reported Friday.

The Moroun-backed ads suggest that Michigan risks being saddled with big debts from the bridge – or that the money being spent on it should be used for police service, firefighting or education instead. One ad implies, but does not say, that Chinese steel might be used in its construction.

The reality, however, is that a private company will build the bridge and Michigan won't have to put up a cent for the span or for the infrastructure on the U.S. side to connect to it. Canada is so eager for another bridge to ease bottlenecking and meet future growth that it is covering Michigan's share of the road approaching the new bridge from the Detroit side – to be repaid from toll revenue years later.

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"Canada bears all costs and all liability for the project and ... Michigan bears none," Mr. Norton told a crowd of 300 on Oct. 15 at the Crystal Gardens Banquet Center in a Detroit suburb.

"That, of course, is not what the Moroun-financed TV advertisements say. But nothing in those advertisements is true. Nothing," he said.

By the time Nov. 6 arrives, Mr. Norton will have given more than 40 pro-bridge speeches in two months, telling Michigan voters of the benefits that would accrue to them from the span.

The veteran diplomat didn't pull his punches when criticizing the Moroun family while speaking to the Detroit-area Southern Wayne County Regional Chamber last week.

"In no developed country have I ever seen such blatant and comprehensive efforts by a single special interest to bend an entire population to its will," he told his listeners.

"Perhaps I am just a naïve Canadian diplomat, but I find the Morouns' willingness to spend any amount of money to tell any lie to be both shocking and reprehensible."

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Mr. Norton's blunt speeches are getting under the skin of the Ambassador Bridge camp.

"It is quite mystifying that diplomat Norton would actively influence the outcome of a Michigan election," Mickey Blashfield with "The People Should Decide" ballot committee said.

The foreign service officer is making no apologies, noting Ottawa is not buying TV ads in Michigan.

"The Morouns had better understand, however, that if they persist in lying about the agreement that my government has arrived at with the state of Michigan, we will continue to take very free opportunity to tell the truth about that agreement," he told the Detroit crowd Oct. 15.

"The Morouns can try – but they cannot intimidate the government of Canada."

The challenge for Mr. Norton is convincing Michigan voters outside Detroit. Motor City's population may grasp the benefits of a second lifeline for trade in sectors such as the auto industry, but residents elsewhere are less aware of how dependent their state is on commerce with Canada.

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Frank Maytner, a retired Detroit resident who attended Mr. Norton's speech, said he's not sure how he'll vote on Proposal 6. "I think the average man on the street is convinced we don't need the new bridge. That's my feeling but you don't know. Some of those ads – they might be inflammatory – but you'd be surprised how people pick up stuff like that."