Complex sentence: Gallacher lost his West Fife seat to the Labour Party at the 1950 General Election, coming third behind the National Liberal candidate, but remained in politics and served as President of the CPGB from 1956-1963.
Split into simpler sentences: Gallacher lost his West Fife seat to the Labour Party at the 1950 General Election, coming third behind the National Liberal candidate. He remained politically active serving as President of the CPGB from 1956-1963.