Today may go down as the worst day in the life of Gilles Duceppe as leader of the Bloc Québécois.
The expected adoption by the House of Commons of a Conservative motion recognizing that Quebecers make up a nation within a united Canada is likely to blunt one of the most potent weapons left in the sovereignist psychological arsenal.
There is not one federalist leader on Parliament Hill and in the National Assembly who will not find it easier to make the case for Canada in Quebec on the strength of this motion.
Its adoption also makes the possibility of another referendum more remote, even if the Parti Québécois comes to power after the upcoming provincial election.
And it is the result of a gross miscalculation on Duceppe's part.
When the Bloc decided to bring the issue of Quebec's national character to the floor of the Commons last week, it fully expected to wreak havoc in federalist ranks.
In his worst nightmares, Duceppe never imagined that the Prime Minister would pick up the gauntlet or that the other parties would rally behind him.
Now, it looks like the Bloc has squandered a key argument in the long battle for the hearts and souls of Quebecers in a failed attempt to score cheap political points.
In the process, it has also legitimized the notion that the rest of Canada has a say in the definition of Quebec's political character.
Last week, PQ leader André Boisclair scrambled to put the best possible face on this unforced error.
He stated that the parliamentary recognition of Quebecers' national character would eventually make it easier for a sovereign Quebec to be recognized on the international scene.
What Boisclair did not say is that the adoption of the motion will make it harder for his party to stage another referendum - or at least one that it can be confident of winning.
In the debate over Quebec's future, symbolism has always trumped division-of-power issues. Until this motion, the sovereignists had entered that field with the advantage.
Without the failure to enshrine Quebec's distinct status in the Constitution in 1990, there would not have been a second referendum or a close vote on sovereignty in 1995.
The sense that Canada is so wary of Quebec's aspirations that it cannot recognize its fundamental nature continues to fuel the sovereignty movement, despite its two consecutive referendum failures.
Today's motion - symbolic as it may be - amounts to cutting off that fuel line.
It also places Canada on the leading edge of the international debate on federalist arrangements.
In the post-Cold War era, the concept that a people can form a nation without requiring all the attributes of a state, and the accompanying one that different nations should be able to live together under the same political roof, have emerged as compelling elements of an alternative model to a world fragmented along narrow ethnic lines.
Spain, which has recently extended national recognition to Catalonia, is finding that it has taken the steam out of that province's secessionist movement, enhancing its own national integrity in the process.
Today, the Bloc will vote for a federalist motion that stands to deflate its cause, an extraordinary twist in an unexpected saga.
In the past, the party has voted against parliamentary motions dealing with the recognition of Quebec's national character.
After the referendum, sovereignist MPs opposed a Liberal resolution that called on the federal government to take Quebec's distinct character into account in its decisions.
But this is different. The distinct society concept was a federalist idea borne out of the desire for a constitutional reconciliation.
From the start, sovereignists dismissed it as an anemic reflection of Quebec's reality.
For years, their leaders have claimed that Quebecers should accept nothing less than the recognition by the rest of Canada that they make up a nation. They have also claimed that it would never happen.
But by the end of last week, Duceppe found himself in a trap of his own making, caught between supporting a federalist consensus on Quebec or voting against a concept he and his fellow sovereignists have promoted.
And so, on the core question underlying the Quebec/Canada debate, that of Quebecers' national identity, the Bloc will stand shoulder to shoulder with MPs from all parties and from across Canada today.
After 16 years, it does seem the Bloc has come full circle. The party wanted to bring the sovereignist battle to Parliament Hill; it has ended up handing new weapons to its federalist foes.