A
Liberal politician, Mitchell was first elected as a
Member of the Legislative Assembly in a by-election in
Medicine Hat provincial electoral district on June 29, 1910, after
Premier Arthur L.W. Sifton appointed him to the cabinet on June 1. Mitchell held two cabinet portfolios as the Minister of Education and the Attorney General of the province. He would serve both portfolios for 2 years until he became Minister of Public Works on May 4, 1912, and dropped the others. In the
1913 Alberta general election Mitchell lost his seat to
Nelson Spencer from the
Conservative Party. Mitchell was the only Cabinet minister defeated that election, but his was one of a few high-profile defeats across the province. After his defeat in the 1913 general election,
George Lane, the MLA for
Bow Valley, resigned to provide a seat for Minister Mitchell. On June 12, 1913, he was acclaimed and again rejoined the government. He would serve Bow Valley as its MLA until his resignation in 1926. Mitchell was reappointed to the Sifton Cabinet as the provincial Treasurer on November 28, 1913. He became the first Treasurer in Alberta history not to serve simultaneously as premier. He held that position until the
United Farmers of Alberta defeated the government in
1921. On April 29, 1920, Mitchell was appointed to be Minister of Municipal Affairs, in addition to being the Treasurer. ==Defeat of government==