John J. Sullivan was a Hamilton, Ontario lawyer and ran for the leadership of the Ontario Liberal Party in 1950. He was best known for having defended Evelyn Dick in one of the most notorious murder trials in Canadian history in 1946 - she was charged after her missing husband's torso was discovered with his head and arms having been sawed off. Sullivan defended her at her initial murder trial in which she was convicted and sentenced to hang.
Sullivan ran in the 1950 Ontario Liberal leadership convention but was eliminated on the first ballot after coming in eighth place with four votes. He ran as a left-wing Liberal arguing that the party should appeal to "the working man" and that Liberals traditionally won elections when they ran to the left.