MONTREAL -- When Bloc Quebecois Leader Gilles Duceppe appears in the leaders' TV debate tonight, expect him to spend much of his time attacking one rival: the NDP's Tom Mulcair.

With the NDP appearing to have maintained much of its momentum in Quebec since its 2011 electoral breakthrough in the province, the longtime sovereigntist leader will no doubt view the two-hour French-language debate as a golden opportunity to put a dent in Mulcair's armour.

The NDP won nearly 60 of Quebec's 75 seats in Quebec in 2011 under Jack Layton, reducing the Bloc to a rump of four.

This time around, there's even talk the Bloc may be shut out and University of Ottawa political science professor Francois Rocher says Duceppe has to focus on targeting the NDP leader.

"He has to perform relatively well in attacking Mulcair and explaining why the Quebec electorate has something to gain in sending to Ottawa a bunch of (pro-independence) MPs," Rocher said in an interview.

"In the current state of affairs, the Bloc won't be able to elect even one MP member, so the biggest winner might and should be, if there is any, Gilles Duceppe."

One surefire topic during the debate will be the wearing -- or not -- of niqabs at citizenship ceremonies.

The polarizing issue has surged to the forefront of the campaign as of late, with Duceppe adamant the garb should not be allowed at such events.

He came out this week in favour of invoking the notwithstanding clause to buttress legislation to ban the wearing of niqabs at citizenship ceremonies.

Rocher believes Duceppe will be a winner if he hits the subject hard.

"I expect this topic will be covered because it is a good way for the Bloc to distinguish itself from the NDP and to restate in a sense the position taken by the sovereigntist political actors, or elite, over the past two or three years.

"And then it will be in line with the general feelings of the Quebec electorate, so Duceppe has everything to win in focusing on that issue."

Mireille Paquet, an assistant professor in Concordia University's political science department, said niqabs and pipelines will be on Duceppe's radar but that there is also a bigger picture for the Bloc leader.

"The debate is really all about showing he is not irrelevant and that the Bloc Quebecois is not irrelevant to Quebecers anymore," she said in an interview.

"He doesn't have a lot to lose but he does have a lot to win if he can renew that romance he had with voters once upon a time."

After winning the four seats in 2011, the Bloc has had a tumultuous time, including Duceppe's resignation, Mario Beaulieu's appointment as leader, subsequent defections, Beaulieu's departure and Duceppe's return.

The Bloc leader will also be hoping to impress any voters in his riding of Laurier-Sainte-Marie. By all accounts, Duceppe is in a dogfight with NDP incumbent Helene Laverdiere, who upset him in 2011 after he had held the riding since 1990.

Duceppe, who has been excluded from this campaign's English-language debates, is fond of saying he prefers taking part in the English events and that pundits have said in the past he has won some of them.

"That (preferring the English debates) surprised people but I would tell them, 'The reason is simple. I understood everything they said in English but I didn't necessarily understand everything they said in French,"' he said at a campaign stop Tuesday in Saint-Hyacinthe, triggering the usual widespread laughter.