Three federal byelections in Quebec scheduled for Monday have the main political parties on edge after tight races in at least two of the ridings.

Liberal member of Parliment Ken Dryden shares a laugh at a campaign event in Jocelyn Coulon's Outremont riding Saturday.
(David Boily/Canadian Press)

Voters are heading to the polls in St-Hyacinthe-Bagot, Roberval-Lac-St-Jean and Outremont.

The Roberval-Lac-Saint-Jean riding has been a Bloc Québécois stronghold for 15 years, but in the last election, the Bloc won it by only 3,000 votes.

Pundits say there's a sense in the riding that the Conservatives could win for a couple of reasons: they finished a close second last time and now are no longer facing Bloc stalwart Michel Gauthier, who has retired from politics.

The Tories' candidate in Roberval-Lac-Saint-Jean is the mayor of Roberval, Denis Lebel.

Provincially, St-Hyacinthe-Bagot is held by Claude L'Écuyer of Action démocratique du Québec. In the federal contest for the agricultural district, he came out in support of Conservative Bernard Barré, but polls have suggested the Bloc could still hold on to St-Hyacinthe-Bagot, vacated with the resignation of the Bloc's Yvan Loubier.

Elsewhere, the Liberal stronghold of Outremont in Montreal could fall to the NDP. A Unimarketing poll released on Friday showed the party's candidate, former provincial Liberal cabinet minister Thomas Mulcair, had 38 per cent of voter support, compared to 32 per cent for Liberal Jocelyn Coulon.

A victory for Mulcair would give Quebec only its second NDP member of Parliament. The party won its first seat in a 1990 byelection.

Letting Outremont slip away would be a major blow to federal Liberal Leader Stéphane Dion, whose party is facing its first ballot test since he was chosen as Liberal leader last December.

"My leadership is solid," Dion said on Saturday when asked whether the byelection is also a personal evaluation. "We are a united party and we are working for victory."