MONTREAL — Stephen Harper's carefully crafted indifference in the face of persistent attacks seemed set in stone through Monday's debate.

And then Prime Minister Paul Martin suggested an astonishing change to the supreme law of the land.

The Conservative leader alternated between serene smile and gentle frown for much of the encounter.

"My strengths are not spin or passion,'' Harper told the camera.

But as Martin dove into uncharted constitutional waters, Harper's emotions seemed to run the gamut from A to B; from raised eyebrows to a surprised and satisfied grin.

When the prime minister proposed eliminating Ottawa's right to override the Charter of Rights and Freedoms, all of Martin's rivals stopped taking notes or staring into the distance as they realized their rival had made news.

The Bloc's Gilles Duceppe and NDP Leader Jack Layton stiffened and cocked their heads toward Martin, as if to make sure they were hearing him correctly.

The gamesmanship vanished.

It was barely there from the start.

There were no yuks, no quips and no forced bonhomie from grim federal leaders in the moments before the debate.

Pre-debate humour from Steve Paikin, the television host and rookie English debate moderator, was met with stony silence.

"You've all done this before, got any tips for me? I've never done this before,'' said Paikin, a TV Ontario broadcaster.

His attempt at self-deprecation was met with studied indifference. Martin and Layton gazed at their notes with furrowed brows. Duceppe appeared to mouth his opening statement in response.

Harper, who gazed serenely into space instead of studying his notes, snapped out of the zone to offer Paikin some comfort.

"You have someone in your ear, (helping you out) which could be helpful,'' Harper said.

"Or not, I guess.''

The intense, business-like environment differed sharply from last month's debates in Vancouver. Those encounters were preceded with banter about water consumption and aching feet.

These men knew what was at stake. Careers were in the balance. The direction of the country was at stake.<

Early blows were aimed at the tax practices of Martin's family business. Harper was called upon to defend his views on the charter.

Harper responded to barbs with a weary smile and an attempt to rise above the fray.

When Martin accused Harper of delivering "drive-by smears,'' Harper's smile turned upside down. He aimed a pained gaze into the darkened studio behind the cameras.

While under attack, Martin shifted on his feet and alternately furrowed and raised his eyebrows.

The future of Canada was the fuel for the liveliest exchange of the evening, as Duceppe badgered Martin to describe Quebec as a "nation.''

When Martin went into verbal contortions to avoid saying the word, Duceppe shook his head and pursed his lips.

With the final seconds running out on the clock, Martin finally blurted out the word, without directly calling Quebec a nation.