The delegates had worked for 36 hours straight at the international gathering in Montreal in 2005 intended to keep the Kyoto Protocol from stalling. The deadline to adjourn had passed, and so had a long night of high drama and low obstinacy.

Stéphane Dion.

In the bleary dawn of 6 a.m., as the translators threatened to pack up and the janitors hovered to sweep the hall, conference chairman Stéphane Dion got what he wanted — a stubborn Russian gave in and the reluctant Americans signed on. Afterwards, the participants lined up to shake his hand. Among them was Bill Hare, the veteran representative of Greenpeace, usually the harshest critic of the establishment.

“I had never seen Hare do that,” said Steven Guilbeault, who represented the Canadian delegation of Greenpeace. But Dion deserved the praise, he said: “The whole thing could have collapsed.”

The praise for Dion, then Canada’s environment minister, helped catapult the lanky former professor into the leadership ranks of his party and, three years later, into the brawling campaign to be Canada’s next prime minister.

When Canadians go to the polls Oct. 14, they will choose from among four national candidates, with the contest led by Prime Minister Stephen Harper — a conservative from Alberta’s oil patch who has snubbed Kyoto — and Dion, who staked his political future on the accord.

For Dion, 53, it has been a torturous campaign. His environmental proposals have fallen flat, he has been mocked and ridiculed by his opponents, undercut by his political allies, and he faces the prospect of a stunning defeat that may make him one of the few Liberal Party leaders never to become an elected prime minister.

Dion insists he has faced political catastrophe before. “I have been underestimated,” he has said. “It’s my weakness. At the same time, it’s my strength.”

Indeed, the irony of this campaign is that Harper’s Conservative Party has managed to portray Dion as weak and indecisive in spite of a political biography that reflects just the opposite. Dion has stubbornly hewed to the course he thinks is right, even when it was politically toxic.

That trait brought him to public notice in the early 1990s, during one of the periodic flare-ups of the Quebec independence movement. Dion, the son of a noted Quebec political scientist, was teaching at the University of Montreal. He weighed the heated calls of Quebec separatism and decided it was better for the province to remain part of Canada’s federation. It was a highly unpopular view in Quebec.

“I remember the debates on separatism,” said Guilbeault, then a student at the university. “There would be a long line of people waiting to speak on the side of ‘yes’ for separatism. And on the other side, there would be only one person: Dion.”

Dion’s scholarly defense of federalism won the notice of then-prime minister Jean Chretien, who persuaded the reluctant academic to join the cabinet. But it also won Dion bitter condemnation in Quebec. For years, he was drawn as a rat in political cartoons, and described by the French-speaking press as a traitor.

“They even had to post security guards outside of his mother’s house,” said Laurent Arsenault, a friend and high school classmate. “That bothered him. Why do they threaten my mother? he said. But it also lit his fire even more.”

He was an awkward fit in back-slapping political circles. He showed up to join the cabinet with a cheap nylon backpack he had carried back on the campus in Montreal; an amused colleague bought him a leather one. He was more comfortable with academic argument than with the political jab and sound bite. Friends insist he has a quirky sense of humor, but Dion appeared humorless in public. He once famously reprimanded Chretien for not being serious enough.

So he was not considered a strong contender when the Liberals, long the dominant party in Canada, met in December 2006 to pick a party chief to try to regain the government they lost that January to Harper’s Conservatives. But the two top Liberal candidates bucked into a stubborn deadlock at the party convention, and Dion squeezed past them on the fourth ballot; an “accidental winner,” pundits quipped at the time.

Accidental or not, Dion seemed to some the right man on the right horse. Throughout 2007, the environment was at the very top of Canadian voters’ concerns, according to the polls. The country seemed ready for action on the Kyoto Protocol. Dion unveiled an ambitious plan of taxing sources of carbon dioxide — from natural gas to heating oil to diesel fuel — coupled with a cut in business and income taxes. The net result would be a savings for many Canadians, he said, and would bring a historic “green shift” from taxing income to taxing pollution, he argued.

But Harper pounced. His party mounted a series of attack ads. Canada Press, the usually careful news service, compared the approach to “taking a flamethrower to Dion … and it has not stopped for 19 months.” Harper railed that Dion’s Green Shift plan is a crushing new tax that would send the country into recession and divide Canadian provinces.

To the dismay of his supporters and environmentalists, Dion has been unable to recover. The economic clouds in the United States have made Canadian voters nervous, and Dion has failed to convince them the Green Shift would not hurt them economically.

“Most people don’t understand it,” said Vancouver pollster Angus McAllister, who has tracked attitudes on the environment for many years. “They just hear the word tax. They don’t even understand why Dion wants to tax carbon. You give them a multiple choice and they even get it wrong.”

The polls have put the Conservatives 13 or more points ahead of the Liberals, who have lost supporters to other left-of-center parties — the New Democratic Party, the Greens, and the Bloc Quebecois.

“If there were only one opposition party, Harper would be defeated,” McAllister said. But Dion has been unable to prevent the splintering of his allies.

“It’s the agony of being Stéphane Dion,” said Andrew Cohen, an author and political commentator at Carlton University in Ottawa. Dion, bespectacled, thin and publicly awkward, has become a victim of the Conservative caricature, Cohen said, in part because of his language. Although all the candidates in officially bilingual Canada must speak both languages, Dion’s English is delivered with French syntax and a heavy accent. He “doesn’t have an ear for the music of the language,” said one pained listener.

“In fact, Mr. Harper, he speaks better English than me,” Dion conceded at a campaign stop in Halifax last month. “OK. But I say the truth better than him in English and in French.”

In a last effort to avoid a landslide, Dion has tried to move the topic of the campaign away from his Green Shift. He spent much of last week’s nationally televised French and English debates in Ottawa promoting a new economic plan.

It picked up a few points in the polls, but some believe that is too little too late. Faced with the threat the Conservatives will win a majority control of the parliament, even some of Dion’s competitors have come to his defense.

“He is certainly brilliant,” Green Party leader Elizabeth May offered recently. “He’s kind, and he’s decent, and he’s honest. And I hope that doesn’t make him unfit for politics.”

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