Complex sentence: Adelaide is the only federation seat in South Australia which continues to regularly change hands, though it was in Labor hands for all but six years from 1943 to 1996, including a 23-year Labor hold during the Robert Menzies era.
Split into simpler sentences: Adelaide is the only federation seat in South Australia which continues to regularly change hands. However, Labor held it for all but six years from 1943 to 1996, including a 23-year Labor hold during the Robert Menzies era.