The political ghost of failed Labor leader Mark Latham hovers over September’s federal election. Recall that it was only the ‘Latham factor’, resulting in the doubling to 360,000 in the number of ballot papers deliberately left blank or adorned with generally uncomplimentary scribbled messages, that saved Julia Gillard three years ago, especially in NSW where Tony Abbott’s failure to win key seats cost him the election.

The voting behaviour revealed in the Australian Electoral Commission’s detailed study of the 2010 election’s informal vote tells the story: in losing enough seats to wipe out her majority in the House of Representatives, Gillard only avoided the loss of several more because a record number of disillusioned Labor voters chose to follow Latham’s controversial advice on national television to cast a deliberately informal ballot rather than to take that extra step to the Coalition.

What happens next September to these deliberately informal ‘protest votes’ of traditional Labor voters will determine the outcome in the crucial seats, especially in western Sydney, that are needed to win government. Abbott must follow the lead of John Howard federally, Barry O’Farrell in NSW and Campbell Newman in Queensland in convincing them to make that last leap.

Labor has good reason to be worried about what these disillusioned voters will do after three years of Julia Gillard. Internal polling reported last November by Fairfax media indicated that ten Labor seats in NSW, predominantly in western Sydney, could fall. It listed two ministers, Chris Bowen in McMahon and Tony Burke in Watson, as being in the firing line, with Jason Clare in Blaxland facing a ‘close call’. This may explain Clare’s recent intervention on the state issue of crime in western Sydney and Julia Gillard’s all-talk-but-no-funding announcement of a Clare-led investigation into ways to reduce suburban violence and crime. Meanwhile the discredited NSW state Labor machine is seeking to restore its traditional working-class links by moving its head office from Sydney’s CBD to the western suburbs.

There is no doubt this doubling of blank ballot papers nationally (with a trebling in Queensland) which helped lift the total national informal vote by 40 per cent to an abnormal 5.5 per cent in 2010, presents serious problems for Labor, particularly in its western Sydney heartland. This semi-flexible vote (much of which apparently did go to the Liberals in the 2011 NSW state election) exceeds the swing needed next September to lose several marginal as well as formerly ‘rusted-on’ Labor seats. In Greenway the 3.7 per cent deliberately informal vote spells death where it only takes a swing of less than one per cent to lose the seat.

And the same goes for Lindsay with a three per cent deliberately informal vote, three times Labor’s one per cent margin. Banks and Reid are now in the equation, with Labor’s majority in Banks of only 1.5 per cent being less than half the deliberate informal vote of 3.4 per cent, and Reid’s margin of 2.7 per cent being well below the 3.3 per cent of deliberate informals. When other NSW seats are added to the list, such as Robertson whose one per cent margin is way under the 2.5 per cent deliberately informal vote, the challenge for Abbott and the crisis facing Labor are laid bare even before considering how much of the anti-Labor swing in the 2011 NSW state election may carry over to the federal poll. The same goes for Queensland, although there the bulk of marginal seats are held by the Coalition

The much higher volume of deliberately informal votes, exceeding five per cent, in safe Labor seats like Blaxland and Watson (which pushed the total informal vote, including unintentional mistakes, well into double figures) demonstrates the depth of Labor’s heartland problems, with others listed by the AEC in the big league for deliberately informal votes in western Sydney being Fowler, Chifley, McMahon, Werriwa, Barton and Parramatta.

Not only does the record number of deliberately informal votes of 2010 contain the potential to change the government, it also puts the lie to recent Liberal complaints that ‘compulsory voting is undemocratic’. In reality, there is no compulsion to vote for anyone; there is nothing illegal about voting informal, or even encouraging people to do so. The distinction between being required by law to vote and yet being able legally to avoid voting for anyone was demonstrated by Mark Latham, who satisfied his desperate need to overcome what former Labor Foreign Affairs Minister Gareth Evans described as ‘relevance deprivation syndrome’ by proposing on national television during the 2010 election campaign that Australians follow his lead by turning up at the polling place, having your name checked off and then simply inserting a blank ballot paper in the box. It is, he said, ‘the ultimate protest vote’.

While the Electoral Act requires Australians to register to vote and to attend a polling place, defines what are formal and informal votes and lists penalties for misleading or deceptive conduct that ‘might lead a voter to fail to record a valid vote’, Latham was in the clear, as an AEC spokesman confirmed; his conduct (in this case, at least) was not ‘misleading or deceptive’, even though he clearly sought to subvert the intentions of the Act. There simply is nothing in the Electoral Act to prevent a P.J. O’Rourke ‘don’t vote, it only encourages the bastards’ public campaign.

Even without these record numbers of deliberate protest votes, Labor faces the risk that at least some of the huge anti-Labor state election swings, particularly in NSW and Queensland, will carry over to September, despite the lack of a convincing historical correlation. The size of this potential threat to federal Labor is shown in a background paper by the ABC’s Antony Green for the NSW Parliamentary Library which shows falls of up to 40 per cent in Labor support between the 2010 federal election and the 2011 NSW state election in comparable booths. As a mini-swing of only 1.5 per cent would see Labor losing four of its NSW marginal seats (Greenway, Robertson, Lindsay and Banks, all of which also have margins below their deliberately informal protest vote), any carry-over from the state numbers would be fatal. And then there are rural seats like Page where Labor’s vote was halved.

There is nothing new about deliberately informal ballot papers; as a member of the House of Representatives I received lots of advice written on informal ballot papers suggesting what I should do with them, most of it uncomfortable. But they have never been seen in such huge numbers, nor in so many marginal seats where they exceed that margin; there are 24 electorates, both Labor and Liberal, throughout Australia with margins lower than the 2.7 per cent average of deliberately informal protest votes. Whatever happens in September to this record number of ‘Latham’ ballots, no former leader will have left such a blank political legacy as Mark Latham.

Michael Baume is a former federal Liberal MP and senator.