Thomas Mulcair, a lawyer and former provincial Liberal cabinet minister, won the NDP's only seat in Quebec. ((CBC))

The NDP held on to its only seat in Quebec on Tuesday as Thomas Mulcair came out ahead in a tight race in Outremont with his Liberal opponent Sébastien Dhavernas.

Mulcair, a lawyer and former provincial cabinet minister, first won the Montreal Liberal bastion in a 2007 byelection, benefiting in part from the absence of disenchanted Grit voters who stayed home to protest the sponsorship scandal.

But his narrow victory on Tuesday is the NDP's first in a general election in Quebec and marks a watershed moment for the party, Mulcair said.

"People didn't think we'd be able to pull it off, but we did," he told supporters at a victory party on St-Laurent Boulevard.

Popular support for the NDP in Quebec increased by 60 per cent in this campaign and, though it didn't translate into seats, it's a great result and "a beautiful message," Mulcair said.

"The NDP has a home in Quebec, because Quebec's values are the NDP's values. "It's just a start, just watch us go."

Mulcair, who has served as the party's Quebec lieutenant since his byelection win, helped revive leader Jack Layton's hopes for the NDP in the province.

But he was under pressure in the campaign to show he was more than a protest choice for voters.

Took nothing for granted

"We never took anything for granted," Mulcair said. "We knew we worked hard in the last year, but we knew it had been a Liberal riding for the past 137 years."

The riding includes Outremont, an upscale neighbourhood near the University of Montreal populated by francophones, anglophones, artists and Hasidim.

The riding also covers some parts of the multi-ethnic Côte-des-Neiges and Park Extension districts.

Mulcair was polling more than 10 points ahead of his rival, Liberal candidate and actor Sébastien Dhavernas, by the end of the campaign.

He was frequently parachuted into other promising ridings, including Westmount-Ville-Marie, where former CBC host and NDP candidate Anne Lagacé-Dowson tried to surpass Liberal star candidate Marc Garneau.

Mulcair also spent considerable time in Gatineau shoring up support for Françoise Boivin, who was defeated by Bloc Québécois candidate Richard Nadeau.

The 53-year-old said he's delighted to be a "voice for peace and sustainable development."

In the Liberal government of Quebec Premier Jean Charest, Mulcair had been minister of sustainable development, environment and parks.

Stephen Harper has a long way to go before he wins much Quebec support, he said.

"The Conservatives have got to understand that it's not enough to start your press conferences in French," he said.

Mulcair is the second NDP MP elected in Quebec, after consumer advocate Phil Edmonston (1990).