OTTAWA -- Campaigning Conservatives continued to press the hot buttons Friday, highlighting what they call "barbaric cultural practices" and Muslim facial coverings amid evidence the tight, three-way election race may be starting to break loose.

The NDP, which appears to be getting squeezed in national public opinion surveys over the past two weeks, is fighting back with a proposal to protect voters' rights -- hoping to reignite public dismay with Conservative changes to the elections act and remind voters of Prime Minister Stephen Harper's decade-long record in office.

But it is cultural identity issues that have inflamed the election discourse since mid September and all evidence points to an invigorated Conservative campaign comfortable with cranking up the heat in advance of tonight's final, French-language leaders debate in Montreal.

The debate, hosted by the TVA network, comes amid recent polls that suggest New Democrat support in Quebec is loosening, giving the other parties an opening.

Chris Alexander, the Conservative immigration minister who's facing a tough Liberal challenge in his Toronto-area riding, held a news conference Friday to remind the electorate of last November's "Zero Tolerance for Barbaric Cultural Practices Act," and to promise even more government resources if re-elected, including a proposed RCMP tip line where people could report "information about incidents of barbaric cultural practices in Canada."

Alexander directly linked the message to a proposed Conservative ban on women wearing facial coverings at citizenship ceremonies, the so-called niqab debate that targets a tiny subset of Muslims and has roiled Internet comment boards with hate-filled, racist rants.

"We need to stand up for our values," said Alexander. "We need to do that in citizenship ceremonies. We need to do that to protect women and girls from forced marriage and other barbaric practices."

NDP candidate Paul Dewar, the party's foreign affairs critic, called Alexander's reprise of the barbaric cultural practices theme "just another example of Stephen Harper's efforts to inflame tensions and divide Canadians for partisan gain."

"This kind of irresponsible dog-whistle politics has no place in Canada," Dewar said in an email.

In Halifax, Conservative Jason Kenney stoutly defended his party's policy -- since rejected by the courts -- of banning the wearing of niqabs at citizenship ceremonies.

"Let's be clear," said the former Conservative immigration minister who now holds the defence portfolio. "This practice of face covering reflects a misogynistic view of women which is grounded in medieval tribal culture."

Kenney also defended the government's move to strip convicted terrorists of their citizenship -- while saying the punishment will not be extended to other criminal acts.

"We will not be pursuing any other legal or statutory grounds for citizenship revocation, let me be absolutely clear about that," he stressed.

The heated campaign debate over "values" and religious accommodation appears to have spurred more than just anti-Islamic rhetoric in Quebec.

A pair of teens tore the headscarf from a pregnant woman in Montreal this week, causing her to fall on the ground. The incident prompted the Quebec national assembly to pass a unanimous motion Thursday condemning hate speech and violence against all Quebecers.

The National Council of Canadian Muslims said Friday the assault on the Montreal woman should be investigated as a hate crime.

The attack is just the latest this year across the country and "comes at a time when inflammatory rhetoric targeting Muslims has been heightened by a federal election campaign in which Muslim women who wear the niqab have been vilified by politicians," Ihsaan Gardee, the council's executive director, said in a statement.

NDP Leader Tom Mulcair and Liberal Leader Justin Trudeau say women should be able to choose how they dress, which is likely to again draw fire from Bloc Quebecois Leader Gilles Duceppe, as it did in the first French-language debate a week ago.

Duceppe's debate performance could go a long way in determining whether the Bloc can woo back voters who deserted the party en masse in 2011 and migrated to the NDP under Jack Layton.

For his part, Trudeau will try to focus the debate on Canada's moribund economy and his deficit-funded infrastructure spending plan as he did Thursday in Montreal when he promised money for transit projects.

Another hot issue in Quebec is the Trans-Pacific Partnership, with the dairy industry in the province fearing the deal will weaken the supply management system of tariffs and production quotas.

The NDP will be hammering the threat to Canada's dairy industry -- which is centred in Quebec -- in an effort to change the channel on the niqab controversy.

Harper promised on Tuesday to preserve Canada's long-standing protection of the dairy and auto industries and will likely reiterate that pledge during the debate.

Green party Leader Elizabeth May was not invited to participate.