Complex sentence: The party was unable to win any other seats, however, and Froese effectively served as an Independent MLA during his time in parliament--despite being identified as party leader for most, if not all of the period from 1959 to 1977.
Split into simpler sentences: The party was unable to win any other seats, however, and Froese effectively acted as an independent MLA during his time in parliament. He served as party leader for most, if not all of the period from 1959 to 1977.