It was announced today that the Batman by-election will be held on March 17, which is the same day as the state election in South Australia (not to mention the by-election being held in Western Australia to replace Colin Barnett in Cottesloe, although that’s a Liberal lay-down-misere that is unlikely to consume much of our attention). The timeline runs as follows:
Close of rolls: Wednesday, February 14
Close of nominations: Thursday, February 22 (noon)
Declaration of nominations: Friday, February 23 (noon)
Start of early voting: Tuesday, February 27
Polling day: Saturday, March 17
Return of writs deadline: Friday, May 18
The Greens have resolved the internal dispute that raised doubts as to whether Preston social worker and five-time candidate Alex Bhathal would again be their candidate. Liberal state president Michael Kroger has not ruled out fielding a candidate if the party learns of links to anti-Semitic activity on Bhathal’s part, though it’s probably a safe bet that this won’t happen.
Implicit in Kroger’s comments, and indeed much of the other commentary surrounding the by-election, is that the Liberals will boost the Greens’ chances if they stay out of the race. The main reason to think this would be so is that Liberal voters would no longer be guided by the party’s how-to-vote cards, which have lately had Labor ahead of the Greens. With the Greens ahead of Labor on the Liberal card, the Greens got 91.8% of Liberal preferences in Batman in 2007, and 80.9% in 2010; when it was reversed, they got 32.6% in 2013 and 36.4% in 2016. All told, around a third of the electorate’s Liberal voters seem to make a conscious decision to favour the Greens over Labor, while 10% to 20% do the opposite, which will presumably continue to inform their behaviour at the by-election.
That leaves HTV-following Liberal voters, accounting for half the Liberal vote total of around 20%, up in the air. Some might react by voting informally, or not at all, thereby depriving Labor of preferences they would ordinarily receive; while others, who would ordinarily express their fealty to the Liberals by following their card, will instead do so by voting against the party they understand to be the main enemy. However, most will probably follow the card of a right-of-centre minor party or independent, which will again lead them to giving a preference to Labor ahead of the Greens. Taking all that into account, a Liberal no-show is unlikely to influence the final two-party result by more than a few points, with the inevitable qualification that that may well prove decisive in a close race.
For historical perspective, the following table shows averages of primary votes swings at federal and state by-elections contested by Labor since the Greens’ electoral watershed in 2001, broken down into those that were and were not contested by the Liberals or Nationals. Unfortunately, there are only two cases of Liberal-contested by-elections held under Coalition governments, hence the very large average swing against Labor. Even the two exceptions (the Griffith by-election to replace Kevin Rudd in 2014 and, on the same patch of turf, the South Brisbane by-election to replace Anna Bligh in 2012) were unusual in being held within six months of the government coming to power, and thus were unusually strong results for the governing party.
To the extent that these numbers offer a guide, they suggest that the impact of the Liberals’ absence will be fairly subtle. Other things being equal, it appears around half the homeless Liberal vote goes to “others”, a third to Labor and a sixth to the Greens. The “others” are mostly right-of-centre candidates with the same attitude to preferences as the Liberals, so these will eventually split between Labor and the Greens according to a familiar two-to-one ratio.
However, two qualifications should be made. One is that Liberal voters appear to be less shy about plumping for the Greens ahead of rival minor parties and independents in seats where the Greens are strong. Another is the rise in the informal vote when the Liberals don’t contest, which on these numbers looks like at least 2%. Assuming these are normally behaving Liberal voters, this would be enough to knock at least half a point off Labor’s two-party total.