Actually, they lost almost every election for the next 20 years. The little interlude with Joe Clark in 1979-1980 was a joke.
And then an even worse disaster in 1993, for another 10 years in the wilderness. So for 30 out of 40 years they were on the outs, all by trying to be Liberal-Lite. And then they went the way of the Whigs, as it were, when the Alliance took over the party 2003-2004. The “Progressive” part finally got a decent burial.