The Bloc Québécois is using gun control to curry favour in a pair of federal byelections Monday that are seen as mid-term popularity contests for the sovereigntist party.

The Bloc is fighting to hold on to the Hochelaga riding in east-end Montreal, and the Montmagnuy-L'Islet-Kamouraska-Rivière-du-Loup riding in eastern Quebec, two regions where its candidates face close races with their opponents.

'We used to finish behind the Marijuana Party [in Quebec]. But we're now real players, so much so the Bloc's even attacking us. Holy mackerel. We must be doing something right.'

—NDP Leader Jack Layton

In Hochelaga, Daniel Paillé, a former Parti Québécois cabinet minister, is fighting off NDP candidate Jean-Claude Rocheleau.

In Montmagny-L'Islet-Kamouraska-Rivière du Loup, Bloc candidate Nancy Gagnon faces stiff competition from former La Pocatière mayor and Conservative Party candidate Bernard Généreux.

The Bloc is using the gun registry as its main byelection issue, especially in Montreal, where brand new election posters went up late last week playing on weapons control.

The posters look as if they've been riddled by bullets, and say the NDP and Conservatives are cut from the same cloth.

The imagery hints back to a key House of Commons vote on the long-gun registry last Wednesday.

Twelve NDP and eight Liberal MPs voted with the Conservative caucus to support a private members' bill proposing elimination of the contentious registry.

Gun control is an important issue in Quebec, where as many as nine out of 10 Quebecers were in favour of the registry when it was initially proposed, said Christian Bourque, vice-president of Montreal-based Léger Marketing.

The registry is just the kind of wedge issue the Bloc has been hoping for, Bourque suggested.

"Usually the Conservatives are a pretty easy target for the Bloc Québécois, in the sense of depicting them as this Western Canadian party that's on the right wing, that tends to be like Americans in many ways," Bourque told CBC News. The long-gun registry vote last week bolsters that strategy, he said.

The New Democrats are hoping the byelections will help them gain ground in Quebec, where they have worked hard to make inroads ever since Thomas Mulcair's 2007 surprise byelection victory in Outremont.

'Holy mackerel. We must be doing something right.'

The NDP doesn't hide its ambition to become the federalist alternative to the Bloc in Montreal.

"We used to finish behind the Marijuana Party [in Quebec]," said NDP Leader Jack Layton last week. "But we're now real players, so much so the Bloc's even attacking us. Holy mackerel. We must be doing something right," he said.

All four federal byelections are seen as sufficiently tight that they could produce upset victories Monday.

B.C.'s New Westminster-Coquitlam is a dogfight between the NDP's Fin Donnelly, a popular local councillor, and the Tories' Diana Dilworth. The Conservatives held the riding until losing narrowly to the NDP in 2006 and again in 2008.

In Nova Scotia's Cumberland-Colchester-Musquodoboit Valley, Casey represented the riding as a Tory for 10 years before being punted from the government caucus in 2007 for publicly criticizing the budget.

Casey won as an independent in 2008, scooping up a whopping 69 per cent of the vote.