Complex sentence: It was formed by Bob Heffron after he and Carlo Lazzarini attempted to depose the party leader Jack Lang and subsequently lost their Australian Labor Party (ALP) endorsements for the 1938 election.
Split into simpler sentences: It was formed by Bob Heffron after he and Carlo Lazzarini lost their Australian Labor Party (ALP) election endorsement. They had been dis-endorsed after attempting to depose the party leader Jack Lang prior to the 1938 election.