In Australian politics, a leadership spill is a declaration that the leadership of a parliamentary party is vacant and open for contest. A spill may involve all or some of the leadership positions. Where a rival to the existing leader calls for a spill it may also be called a leadership challenge. When successful, it is often said that the former leader has been "rolled". In Australian English the colloquial use of the word "spill" seems to have begun in the mid-1940s with the contest to replace Prime Minister John Curtin after his death in office on 5 July 1945.