Born in Brighton, England, Murdock first ran for the House of Commons of Canada as the Liberal candidate in the 1921 federal election in the Ontario riding of Toronto South.

Although defeated, he was appointed Minister of Labour in the cabinet of Mackenzie King shortly after the election.

The current MP in the riding of Kent, Archibald McCoig, gave up his seat and was appointed to the Senate of Canada in 1922.

While Minister of Labour in 1923, Murdock was embroiled in controversy after he withdrew funds from the Home Bank of Canada a day or two before its collapse based on information he obtained as a member of the Cabinet.

In 1930, he was summoned to the Senate representing the senatorial division of Parkdale, Ontario on the advice of Prime Minister Mackenzie King.