OTTAWA -- All three major party leaders will campaign in Quebec today, targeting ridings in a key battleground that helped turn the tide for the NDP in 2011.

An orange wave swept that province in the last election, giving the New Democrats 59 seats and helping elevate them to Official Opposition status for the first time.

Today, NDP Leader Tom Mulcair first sets his sights on the Lac-Saint-Jean riding of Denis Lebel, the Conservatives' Quebec lieutenant.

Mulcair then heads to two other ridings the NDP took from the Bloc Quebecois in 2011: Compton-Stanstead and Sherbrooke.

Conservative Leader Stephen Harper also targets one such riding today, delivering remarks in Trois-Rivieres, where the NDP ended 18 years of Bloc Quebecois rule in the last election. The Conservatives came a distant third in that riding in 2011.

Harper will also campaign in Drummondville in the afternoon before visiting Thetford Mines in the evening.

Liberal Leader Justin Trudeau's first stop today is in the new riding of Ahuntsic-Cartierville, a district that was won in 2006, 2008 and 2011 by Maria Mourani of the Bloc Quebecois. Mourani is running again in the riding, but this time under the NDP banner.

The Liberals have fielded a star candidate to run against her: former Montreal mayoral hopeful Melanie Joly. She hopes to recapture the seat for the Liberals, which held it until 2006.

Trudeau's campaign will then head to Laval-Les Iles, north of Montreal. The riding was held by the Liberals until they lost it to the NDP in 2011.

Later in the day, his tour will stop in the new riding of Therese-De Blainville. The district is composed of areas that supported the NDP four years ago.

Green party Leader Elizabeth May heads to Ontario, to campaign in the Guelph riding where the Greens are running star candidate Gord Miller, the former environmental commissioner of Ontario.

The Greens came a distant fourth in the riding in 2011, but the provincial Green leader came third in the riding in the Ontario election last year, within striking distance of a second-place finish.

Bloc Quebecois Leader Gilles Duceppe will campaign today in Montreal, Mascouche, Saint-Jerome and Lachute.