Complex sentence: In the party's first election in 1935, it ran candidates only in Western Canada and won 17 seats, all but two of them in Alberta, where it won over 46% of that province's popular vote.
Split into simpler sentences: In the party's first election in 1935, it only ran candidates in Western Canada. It won 17 seats, of which 15 were in Alberta and where it won over 46% of that province's popular vote.