Voters have redrawn Canada's political map, electing as the official opposition a social democratic party that engaged the middle class and made deep gains in Quebec.
"It's dramatically revolutionary," Nelson Wiseman, a political science professor at the University of Toronto, told AFP.
Projections showed the New Democratic Party, led by former municipal politician Jack Layton, capturing 43 percent of the vote in Quebec and more than 30 percent across the country in Monday's poll.
It humbled its three rivals in all-important Quebec, which holds a quarter of seats in parliament, destroying the Bloc Quebecois' separatist hegemony and routing the Liberal Party, historically Canada's strongest political group.
It failed, however, to block Conservative Prime Minister Stephen Harper from winning a majority government, despite limiting his Conservatives to a mere six seats in the Francophone province, only a few more than the Bloc Quebecois.
"The New Democratic Party will now be able to claim that it's the only truly national party," Wiseman said.
The chattering classes scrambled to explain the NDP's meteoric rise in Quebec in a mere five weeks and its ripple effect in the rest of Canada, which has led to a realignment of politics.
At the outset of the campaign on March 25, the NDP had only 12.8 percent support in Quebec, according to an EKOS poll.
But Layton shot to stardom in Quebec with energetic performances in a televised French-language debate and on Tout le Monde en Parle, a current affairs TV program with provincial ratings that rival the Superbowl's.
Layton, who is battling prostate cancer and walks with a cane because of a broken hip, won admiration from cheering crowds for his tenacity and smiling demeanor during the campaign.
The NDP campaigned to raise the corporate tax rate by three percentage points to 19.5 percent -- a return to 2008 levels -- eliminate $2 billion in subsidies to the oil sands industry and implement a cap-and-trade system to control pollution.
It also supports increased spending on health and education.
In contrast, Harper has gradually cut corporate taxes, backed the powerful oil industry and shied away from implementing climate-change legislation.
His critics have meanwhile accused him of subverting parliamentary democracy by withholding information in a budget bill.
The NDP's progressive social policies made it attractive to Quebecers disenchanted with the Bloc Quebecois.
It made further inroads in the province because it pursued "the most aggressive two-nations line" of any federal party, Wiseman said.
"It has advocated a strong central government in Ottawa for English Canada and strong centralized government in Quebec," Wiseman said.
Longtime political activist Judy Rebick attributed much of the NDP's success to its "positive" message.
"People are sick of the old line parties. And Layton has run a relentlessly positive campaign," said Rebick, who teaches politics at Ryerson University in Toronto.
"When Quebec went the way it did, Layton suddenly became the alternative to Harper."
After Layton's TV performances ignited Quebec, his popularity spread like wildfire through social media, according to Henry Milner, a research fellow in electoral studies at the University of Montreal.
"It seems to have been an electronic development, and that's one of the reasons it wasn't obvious," Milner told AFP.
"The social media have been very much the means by which the momentum spread," Milner said.