Hypothetically, how could someone have contributed to Canada's political development from 1867 to World War I?
Canada is two nations held together through political agreements that occured during the 18th Century. Much of Canada was a British colony, while eastern Canada was held by France. Subsequent political and cultural developments in Canada have, consequently, reflected those diverse origins.
France ceded control of its Canadian territory to the English Crown with the signing of the Treaty of Paris in 1763. Ever since, French Canadians have fought politically -- and sometimes violently -- to protect their French heritage, including the public use of the French language in a country otherwise politically dominated by English-speaking descendents of the British.
That the question specifies the year 1867 is no accident. That was the year of the Constitution Act, which established a federal system with a strong central government, and a constitutional monarchy to provide symbolic unity. While the monarch does exercise power in the Canadian political system, Canada is, by and large, run by a parliamentary system of government, wherein the ruling party appoints a prime minister.
During the 19th Century, Canada underwent some of the same growth pains as did those settling the United States beyond the Mississippi. Whereas, in the United States, the migration was westward, in Canada, jin addition to the westward expansion of Canada, there was an English-speaking migration east toward Quebec, which resulted in friction between French settlers and the British, sometimes resulting in violence, most notably, the Red River Rebellion of 1869, which lead to the establishment of the province of Manitoba.
Throughout his period, the Canadians maintained their democratic form of government, with prime ministers being elected or removed from their position. In the meantime, expansion of the authorities of the central government continued, with the continued occasional outbreak of violence as a result. Friction between English- and French-speaking Canadians continued to be a problem, and rebellions against British rule continued to occur. Immigration from Asia and from Eastern and Central Europe brought large numbers of additional people, with large numbers of additional languages and cultures. Many of these immigrants, especially those from Asia, settled in the western part of the country.
The most important Canadian leader in the period leading up to the First World War, was Wilfrid Laurier, who served as prime minister from 1896-1911. More than his predecessors, Laurier sought to forge a more united Canadian identity, including reaching out to the French-speaking population. Toward that end, Laurier moved the government from federal system more toward a confederacy, and began easing it away from the British Crown. Because of continuing pro-British sentiments within the vast English-speaking community, Laurier had to act with great sensitivity toward both proponents of remaining part of Britain and those who placed a premium on alleviating French-speaking Canadians' concerns about being sublimated to the English and who agitated for the confederacy. Consequently, one way a person could hypothetically contribute to Canada's political development during this period is to voice an opinion for or against a more integrated and dominant French-speaking sector in government.
Laurier's policies would lead to the collapse of his government, as pro-Empire factions retained considerable political power. The Conservative government that replaced him was less predisposed to maintain cordial relations with the United States, which fought the British Crown for independence. World War I, with Britain and the U.S. allied, would affect that relationship.