Trudeau was in Brandon on Wednesday drumming up support for Liberal candidate Rolf Dinsdale while Mulcair was doing the same for NDP candidate Cory Szczepanski.
Trudeau says he considers the seat winnable based on what people are saying as the campaign goes door to door.
Dinsdale is the son of Walter Dinsdale, a long-time Tory MP for the riding, and only recently moved back to Brandon from Toronto.
Mulcair says the Liberals are underestimating the NDP.
He has been to Brandon twice since the byelection was called, and says he will return should Szczepanski be victorious.
The byelection is being held to replace Conservative Merv Tweed, who resigned earlier this fall.
Other candidates include Libertarian Frank Godon, a former U.S. marine, and Larry Maguire for the Conservatives.
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