New Democratic Party Leader Thomas Mulcair's belligerent defence of his party's position that a 50-per-cent-plus-one majority in any future referendum will be sufficient to break up the country is irresponsible. In a recent speech in Montreal, he boasted that he is so sure of his stance that he would "wipe the floor" with Liberal Leader Justin Trudeau in a debate on the question. He should show more humility. His position is not well thought out, and it is playing into the hands of Quebec separatists.

Mr. Mulcair, a former Liberal member of Quebec's National Assembly, saw how close Canada came to calamity in 1995, when the No side won by the scantiest of margins – 50.58 per cent to 49.42 per cent. As he continues to remind audiences, that night he saw thousands of No ballots rejected on spurious grounds in his own riding. "Orchestrated, manipulated electoral fraud," is what he called it back then. And yet today he steadfastly insists that a margin of just one single vote, however attained, would be enough to start dismembering the country.

The Supreme Court would beg to differ. Its 1998 ruling on the matter stated that "a clear majority on a clear question" would be required for Quebec to separate. The Clarity Act mirrors that. Mr. Mulcair agrees on the necessity of a clear question. But how can the Leader of the Opposition argue that Canada should consent to being undone by a razor-thin majority, small enough to be considered within a margin of error? It is a ridiculous stance that can't even be defended as democratic; many democracies require supermajorities in plebiscites or legislative votes that have profound national implications. The end of Confederation is as profound as it gets.

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Mr. Mulcair compounds his error when he challenges other federal leaders, especially Mr. Trudeau, to name their percentage. By trying to stir up a dormant debate, he's giving separatists an issue on which to hang their grievances at a time when Quebec is governed by a Parti Québécois minority that never saw an opening it couldn't drive a wedge into.

Maybe it comes down to how Mr. Mulcair sees the Clarity Act. The federal government adopted the law in 2000 to prevent separatists from muscling Quebec out of Canada through emotion, confusion and dirty tricks; the Opposition Leader, hungry for votes in Quebec, is using the Act as a way of currying favour with soft nationalists. It is not a stance to boast about.