Political journalists are often inclined to exaggerate the significance of preference negotiations, but yesterday’s repudiation of the Greens by the Victorian Liberals was an event worthy of the hype.

The Greens’ grand hopes of winning as many as four or even five seats in the lower house are now in tatters, and their chances of securing the coveted balance of power greatly diminished.

The precise extent of the damage is nonetheless unclear, owing to the uncertain extent to which Liberal how-to-vote recommendations translate into numbers on ballot papers.

After the 2006 election, the Victorian Electoral Commission sought to shed light on such matters by conducting a study of ballot papers from eight electorates.

The VEC or those directing it evidently had a particular interest in the Greens’ prospects, as the electorates chosen included the crucial inner-city quartet of Melbourne, Richmond, Northcote and Brunswick.

The respective rate of Liberal voters’ adherence to the how-to-vote cards in these four seats was 38.4%, 30.1%, 42.1% and 45.0%.

While this unavoidably includes voters who independently chose a preference order that coincided with the party’s recommendation, it seems reasonable to infer that at least three in ten Liberal voters were guided by the how-to-vote card.

However, it should not immediately be concluded that this many votes will now flip from the Greens to Labor. It may be that large numbers of Liberal voters were happy to adhere to the card in the knowledge that it observed the party’s age-old practice, and that some might think again now the policy has changed.

As Antony Green notes, there is also a pronounced lack of incentive now for the Liberals to make the effort to circulate how-to-vote cards in the affected electorates, or indeed involve themselves in any other kind of campaigning there.

While Green says he would be surprised if the total rate of Liberal preferences to Labor topped 60%, this would still be a dramatic reversal from the 75% to which they are accustomed — enough to bite into the Greens’ two-party preferred total by as much as 7%.

Booth results from the federal election suggest that even with this handicap the Greens would remain competitive in Melbourne and Richmond. Northcote and Brunswick, however, are now looking beyond their reach.