At the 2004 Senate election in Victoria, the Coalition polled 44.1% (3.1 quotas), Labor 36.1% (2.5 quotas) and the Greens 8.8% (0.6 quotas). The Coalition had a clear three quotas, Labor two full quotas, with Labor and the Greens competing for the final seat seat normally won by the left of politics. Labor's preference deal with minor parties was done to get Labor's third candidate ahead of the lead Green candidate. In the end, Labor's vote was lower than expected, and the preference deal with Family First and other micro-parties put Fielding ahead of the third Labor candidate, resulting in Labor's preferences being distributed instead and electing Steve Fielding. Fielding effectively grabbed one of the left's seats.
In 2010 the circumstances are different. Now it is the Coalition vote likely to fall short of three quotas while Labor plus the Greens will have more than three quotas between them. It is in the interest of both Labor and the Greens to do a tight swap of preferences in the hope that one of them will grab the third seat normally taken by the right of politics. This won't be possible in every state, but if Labor plus the Greens can grab an extra seat in any state, it will have an important impact on the Senate balance of power.
It has to be stressed that this deal won't be responsible for delivering the balance of power to the Greens. Even if the Greens only re-elect their sitting Senators in Tasmania and Western Australia, a re-elected Gillard government would see Labor take seats from the Coalition, and it is the Loss of Coalition Senators elected in 2004 that will pull the Greens Senators into the balance of power. The purpose of the deal is to weaken the Coalition's position beyond what would naturally occur if the Labor government is re-elected.
Of course, if something dramatic happens in the next few weeks and the Coalition wins the election, the Senate position would be different but the Greens still in an important position.
http://blogs.abc.net.au/antonygreen/2010/07/green-preferences-at-the-2007-electi...The Greens WILL hold the balance of power in the Senate
Steve Fielding will be gone - Family First, never to hold a seat in EITHER house again
The Greens are a growing force that the Federal Government (be it Coalition or Labor) will be forced to live and work with