Complex sentence: After the National Party won the 1993 general election with a majority of one seat, Clark challenged Mike Moore for the leadership of the parliamentary Labour Party and became Leader of the Opposition on 1 December 1993.
Split into simpler sentences: After the National Party won the 1993 general election with a majority of one seat, Clark successfully challenged Mike Moore for the leadership of the parliamentary party. Clark became the Leader of the Opposition on 1 December 1993.