He was just a third-place leader in the Quebec National Assembly. His party was tumbling into the teens in public approval, its independence raison d'etre more popular than the crumbling separatists leading the campaign. Given those grim circumstances, Andre Boisclair, leader of the Parti Quebecois, could have slipped from national politics with all the rippling impact of an ocean-plunked pebble. Yet it was the federal Conservatives whose faces were in full beam yesterday, viewing Mr. Boisclair's departure as a potential pick-me-up for their sagging poll fortunes and future election prospects. "It's an OK day," said a grinning senior government official,...