Your challenge, should you accept it, is with any plausible PoD after 1929, have the CCF(Co-operative Commonwealth Federation) win an election and form a government in Canada. Go ahead!
FWIW, "the September 1943 Gallup poll showed the CCF leading nationally with 29 percent support, with the Liberals and Conservatives tied for second place at 28 percent" https://en.wikipedia.org/wiki/Major_James_Coldwell But I don't really know what could make the CCF hold on to that lead.
I attempted a wikibox series based on this idea, but I'm a firm believer that the best they could have gotten was official opposition, and even than they would have lost that support following the next election, much like the Quebec ADQ.