Whatever else might remain unclear about the course of the Queensland election campaign, there is no doubt left that Saturday’s result will look nothing at all like that of three years ago.

During the landslide win that swept Campbell Newman to power, the Liberal National Party vote topped 50% in over half of the state’s 89 electorates, with a statewide primary vote that would have delivered it an absolute majority under all but a handful of electoral systems in operation throughout the democratic world.

But with all indications suggesting the LNP will be lucky if it can keep the swing on Saturday inside of 10%, the actions of minor-party and independent voters in allocating their preferences have re-emerged as a potentially decisive factor.

This fact has been a cornerstone of the LNP campaign, which has run hard with television advertising exhorting voters to “just vote one LNP”.

The curious thing about this message is that it’s not especially directed at those who might end up following the advice. Once the LNP has a voter’s first preference in the bag, it has little reason to care what they choose to do from that point on.

The true objective is to tap into half-understood concerns about the election of senators through preference harvesting, and to propose an exhausted vote not just to LNP voters, but to the electorate at large. From an LNP perspective, the ideal viewer reaction might run: “I’m not voting for that bastard Campbell Newman, but the point about numbering only one candidate is a good one.”

As Antony Green explains, the strategic rationale here is that a high rate of exhausted preferences can only be of advantage to the party with the highest primary vote. Given the modern electoral reality that a solid chunk of the Left vote has cleaved away from Labor to the Greens, this almost invariably means the conservatives.

It was a different story around the turn of the century, when Queensland’s rural and regional conservative vote was being cannibalised by One Nation. At the 2001 election, it was Labor under Peter Beattie that was doing what the LNP is doing now, causing the rate of one-only votes to immediately triple from 20% to 60%, after which it ascended more gradually to a new height of around 70% in 2012.

Clearly Labor is reading the play much the same way, as the overwhelming majority of its how-to-vote cards recommend that voters number every box. The sentiment is being echoed by a union campaign that urges voters to “put the LNP last”.

The minor parties, contrary to the impression given by the LNP advertising, have not actually engaged much in preference trading — and even if they had, the impact of any deals would be limited by a high rate of non-compliance, since the optional preferential system lacks the active ingredient of group-ticket voting that made preference harvesting viable for the Senate.

Nonetheless, the directions that parties offer through their how-to-vote cards very often guide enough voters to determine outcomes in individual seats, and they provide a helpful barometer of how parties see themselves in the broader electoral milieu.

The Palmer United Party is happy to pursue at least one point of commonality with the Liberal National Party, in that it too is making no direction to its dwindling band of followers with respect to preferences.

Katter’s Australian Party, which had far broader ambitions at the height of its powers in 2012, has marked its retreat to the rural political fringe by directing preferences only to One Nation and a scattering of independents of like mind.

As always, though, it’s the Greens who have received the closest scrutiny, particularly from a Labor Party that is quick to feel aggrieved by any indication that the Greens are not doing all they can in the fight against the main enemy.

The Greens are in fact recommending a full suite of preferences in most seats and putting Labor ahead of the LNP wherever they are doing so. But there are a few important exceptions where they have gone the just-vote-one path: in Cairns, Barron River, Mount Ommaney, Nudgee and Woodridge, where their preferences might meaningfully be of use to Labor in unseating LNP incumbents, and also in Maryborough, where former independent member Chris Foley is attempting to recover a seat he lost to the LNP in 2012.

To the question of why the Greens would choose to go easier on the LNP in these seats in particular, the reply would be that the party leaves the matter in the hands of local branches as part of its commitment to grassroots democracy.

This is fine as far as it goes, but it comes with the very substantial downside of producing perverse results when their actions are considered collectively.

The point can be well made with reference to two case studies: the seat of Cairns, which Gavin King won for the LNP from Labor in 2012, and Yeerongpilly, a seat in Brisbane’s inner south, which Leila Abukar hopes to recover for the LNP after its member, Carl Judge, quit the party to sit as an independent.

Abukar came to Australia as a refugee at the age of 19 in 1997, after barely managing to escape violence in her native Somalia that claimed the lives of her father and brother. She went on to work as an interpreter and community advocate while pursuing tertiary studies, ultimately emerging with a master’s degree in international relations from the University of Queensland.

King’s pre-parliamentary vocation was as chief-of-staff with local News Corp paper The Cairns Post, where he had roused controversy by arguing that women raped while under the influence of alcohol were partly to blame for their assault, and describing the federal government’s baby bonus as a “dodgy moneymaking scam anywhere poor people with high libidos reside”. On the occasion of Julia Gillard’s ascent to the prime ministership in June 2010, King asserted in his column that all a woman ever had to do to win an argument with a man was to “say the words ‘pre’ and ‘menstrual'”.

With these CVs in mind, guess where Greens voters are being advised to put the LNP candidate last, and where they are told to take no special stand beyond voting for a Greens candidate who clearly isn’t going to win. Then guess again.

Given that Greens voters are notoriously resistant to the directions of how-to-vote cards, the impact of these decisions should not be overestimated. Nonetheless, voters on the Left in Queensland have good cause to ask if advocating exhausted votes in marginal seats is the best policy when faced by a conservative government towards which the Greens have particularly strong cause to feel hostile.