Dowson and his followers differed with the rest of the Trotskyist movement in Canada through their adoption of a Canadian economic nationalist perspective, influenced by the views of the Waffle, a Marxist tendency within the New Democratic Party (NDP) within which the LSA was active.
Instead, the Socialist League formed the Left Caucus within the NDP and worked to build a leftist tendency within the party.
The group grew initially through the 1970s and was able to recruit a number of student youth, particularly at York University but it declined through the 1980s and became largely inactive after Dowson suffered a stroke in 1989.
Prominent members of the Socialist League included Dowson, Harry Kopyto, Lois Bedard, Gord Doctorow, Alice Klein, Wayne Roberts, Michael Hollett and Ellie Kirzner.
Klein, Roberts, Hollett and Kirzner left Forward in the late 1970s, and founded the alternative newspaper Now Magazine in Toronto.