Did the Libs win the 2010 election because they preferenced the Greens last?

Many psephologists continue to assert that the Liberals won the Victorian state election in 2010 when they made the bombshell announcement that they would preference the Greens last on their How-to-Vote cards. 

This decision is seen as 'decisive' and as turning the election in their favour.

Commentators offer no evidence to support this theory, but it continues to feature as conventional wisdom. William Bowe, who produces the Poll Bludger website, put it this way in a Guardian article on 17 November 2014:

The gambit of putting the Greens in last place decisively energised their [the Liberals] campaign last time, and it comes as no surprise that they have opted to do so again.

The Liberals announced they would preference Labor over the Greens on Sunday 14 November 2010 - just 13 days before the election. Pre-polling would start the following morning.

This was a surprise. They had always preferenced the Greens over Labor previously, diverting Labor resources from marginal Liberal/Labor seats. However, at a federal level the Greens had just entered into an agreement to support the Gillard government, and there was a mood for change.

In 2010 the Liberals went on to win the Victorian election by one seat. Although the Greens came very close in Melbourne, Richmond and especially Brunswick, they did not win any of those lower house seats. They would have won all of them with Liberal preferences, and come close in Northcote.

But did this decision to put the Greens last win the election for the Liberal party?

Labor, through its Griffin report into the 2010 Victorian loss, has released its internal polling in the lead up to the election. The figures are in this graph:

Looking at the figures for 14 November and immediately thereafter, Labor was on 50% two party preferred before the announcement, and then went up to 51 2PP just after it, before dropping back to its 50 2PP thereafter. 

It is clear that the announcement on 14 November 2010 made no demonstrable difference to the figures, and Labor ran very close to the wind all the way to election day. 

In the wake of the coalition's announcement that it would preference Labor ahead of the Greens, no major shift to the coalition can be observed from these figures.

Labor should not have been surprised about their loss in 2010. Their own internal polling told them it was coming. The debacles of MYKI, the desalination plant, channel deepening, and the north-south pipeline cost Labor government - not the Liberals' decision on their how-to-vote cards.

As we move towards the 2014 election, the same preferencing decision will not help the Liberals, and Labor's decision not to reach an accommodation with the Greens will take the edge off a likely victory.