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In Australian politics, a leadership spill is a declaration that the leadership of a parliamentary party is vacant, and open for re-election. A spill may involve all leadership positions (leader and deputy leader in both houses), or just the leader.
A leadership election may result in a new leader, or may confirm the status quo. If the party in question is in government, the election of a new leader will result in a new Prime Minister, Premier or Chief Minister; if the party is the opposition, the election of a new leader will result in a new Opposition Leader.
In the Westminster system, the leader of the party which forms a government becomes the Prime Minister, while the leader of the largest party not in government becomes leader of the Opposition. Contenders for the role of leader of a major party usually (but not always) come from the cabinet or shadow cabinet.
A leadership spill occurs when a member or members of the parliamentary party feel that the leader is taking the party in an undesirable direction or is simply not delivering on their promises to those who elected them, and does not have the numbers to back his or her position. A spill may be triggered by consistently poor opinion polls.
A spill can be initiated by the party leader in office, usually in the hope of gaining a fresh mandate to quell dissenting voices in the party. It may occur at any time, leaving the person in the leadership position always 'on notice'.
- March 1971: Prime Minister John Gorton retained the leadership of the Liberal Party after a challenge from William McMahon resulted in a tie. However, Gorton then resigned, saying that a tie was not a vote of confidence, and McMahon was elected his successor.
- 1981: Prime Minister Malcolm Fraser beat Andrew Peacock's challenge for the leadership of the Liberal Party, 54–27 votes.
- 16 July 1982: Bill Hayden beat Bob Hawke for the leadership of the Labor Party, 42–37 but resigned in February 1983 in Hawke's favor, just one month before the ALP returned to government in the 1983 federal election.
- 9 May 1989: Andrew Peacock won with 44 votes to John Howard's 27, for the Liberal leadership and became leader for the second time. A simultaneous spill took place in the National Party room resulting in Charles Blunt replacing Ian Sinclair.
- 3 June 1991: Deputy Prime Minister and Treasurer Paul Keating challenged Prime Minister Bob Hawke for the Labor leadership, with Keating losing by 44 votes to Hawke's 66.
- 20 December 1991: Keating launched a second leadership challenge against Hawke. This effort was successful, with Keating winning the Labor leadership by 5 votes.
- May 1994: Alexander Downer won 43 votes against John Hewson's 36 votes for the Liberal party leadership.
- 16 June 2003 & 2 December 2003: Two consecutive leadership challenges saw Simon Crean ousted from the Labor leadership, replaced with Mark Latham.
- 4 December 2006: Labor frontbencher Kevin Rudd launched a challenge against Kim Beazley and won the Labor leadership.
- 16 September 2008: Opposition Leader Brendan Nelson lost to Malcolm Turnbull.
- 1 December 2009: Opposition Leader Malcolm Turnbull (Liberal) was defeated by Tony Abbott with a narrow margin of 42–41 votes.
- 24 June 2010: First term Labor Prime Minister Kevin Rudd was replaced by his deputy Julia Gillard, months prior to the 2010 federal election.
- 27 February 2012: Kevin Rudd resigned as Foreign Minister seeking to overturn the 2010 spill result but Julia Gillard retained the Labor leadership with 71 votes to Rudd's 31.
- 21 March 2013: Julia Gillard called a snap ballot following Simon Crean publicly calling for a Labor leadership ballot. Former Prime Minister Kevin Rudd vowed not to stand in the challenge, and as a result Julia Gillard was re-elected unopposed. 
- 26 June 2013: Kevin Rudd retook the Labor Party leadership in a snap spill, defeating Julia Gillard by a 57–45 margin.
- 9 February 2015: A motion to bring about a leadership spill in the Liberal Party is defeated 61–39, with Tony Abbott remaining as Prime Minister.
- November 1996: Premier Dean Brown was beaten by John Olsen for the leadership of the South Australian Liberals.
- April 2007: Martin Hamilton-Smith defeated opposition leader Iain Evans for the SA Liberal leadership.
- July 2009: Two consecutive spills in the Liberal Party led to the ousting of Hamilton-Smith, replaced by Isobel Redmond.
New South Wales
- December 2009: Nathan Rees (Labor) was beaten by Kristina Keneally, to become New South Wales's first female Premier.
- March 2013: Adam Giles replaced Chief Minister Terry Mills as leader of the Country Liberal Party while Mills was on a trade mission, becoming the first indigenous head of government of an Australian state or territory.
- 2nd February 2015: Adam Giles was ousted after a parliamentary meeting voted 9 votes to 5 to replace him with the minister for primary industry and mines, Willem Westra van Holthe. Giles refused to resign and instead promoted Westra van Holthe to the position of deputy leader.
- Bennister, Mark (2012). Prime Ministers in Power: Political Leadership in Britain and Australia. Palgrave Macmillan. p. 73. ISBN 0230273211. Retrieved 27 June 2013.
- "Gillard survives as challenge fizzles out".
- Griffith, Emma; Glenday, James (9 February 2015). "Tony Abbott keeps leadership of Liberal Party but some supporters fear he is doomed". ABC News. Retrieved 9 February 2015.
- "Northern Territory standoff: Adam Giles refuses to step down as chief minister".