“It will be a journey of discovery for Canadians when it comes to Andrew Scheer,” said Tim Powers, the vice chairman of Summa Strategies, a polling and lobbying firm that was formerly an adviser to governments held by the Progressive-Conservatives, one of the predecessors of the current Conservative movement.

Mr. Scheer, 38, emerged from a field of 14 candidates through an unusually complex voting system to take 50.95 percent of the available points. And while Mr. Bernier laid out a detailed and often provocative platform, Mr. Scheer offered few campaign promises that often dealt with small issues. His most significant vow was to end carbon taxes — but that stance was shared by most of the candidates, and such taxes are ultimately a responsibility of provinces, anyway.

Two factors add to the difficulty of predicting what Mr. Scheer will do as party leader now — or what he might do in 2019 if his party defeats Mr. Trudeau’s Liberals and makes him prime minister.

Mr. Scheer was elected to Parliament at age 25 and never served in any of Mr. Harper’s cabinets, which kept his public profile to a minimum. And from 2011 to 2015, he was the speaker of the House of Commons — a job that not only required him to be nonpartisan but also meant he could not propose or vote on legislation.

“Scheer’s advantage is that no one can define him,” said Peter Woolstencroft, a professor emeritus of political science at the University of Waterloo who has written often about Canada’s conservatives. “But his weakness is that he has no defense against people who will try to define him.”