Complex sentence: He became Deputy Leader of the Liberal Party in 1966 and, in 1971, when Prime Minister John Gorton resigned after a leadership vote ended in a tie, McMahon became leader, thus becoming Prime Minister himself.
Split into simpler sentences: He became Deputy Leader of the Liberal Party in 1966. In 1971, when Prime Minister John Gorton resigned after a leadership vote ended in a tie, McMahon became leader, thus becoming Prime Minister himself.