Can you overthink a political campaign?

Not in the modern world of data-driven politics, perhaps.

But seekers of elected office do often overdo it.

Luke Mansillo, a political scientist studying voter behaviour at Sydney University, has concluded that the vast majority of people make up their minds much before the starter’s pistol is fired for a formal election campaign.

His study on the 2016 election found conservative voters made up their minds just after Tony Abbott took power, three years earlier, and when he lost power, months earlier; campaign buses and debates and advertisements were, for most, just a postscript.

The much broader factors affecting an electorate or election, he says – like whether voters have a sense that change can be achieved, or what leads the news at critical times – give strategists their best chance of changing everyone else’s minds.

In the outer-Melbourne seat of Aston on Saturday, a by-election contest has been done to death on cable news but competes for everyone else’s attention with the Australian Grand Prix and AFL.

This weekend it’s the voting system itself that could drive the most change in Aston (it has also shaped our broader politics but much more subtly and slowly).

About 92 per cent of Australians vote in elections under pain of fines. But by-election turnout, especially so soon after a federal election, is a different story.

Voters sometimes register dissatisfaction at by-elections by casting informal ballots (one in five did when Mark Latham quit his federal seat of Werriwa to pursue other interests), while others don’t show up.

The Australian Electoral Commission said that was already happening in Aston where the number of voters at pre-poll booths is down 5 per cent on the federal election last May.

“Typically, if someone casts their vote early in one election, they’ll do so in the next one as well – and we’re not quite seeing that here which makes us worry about low participation,” commissioner Tom Rogers said.

Whose advantage?

Mr Mansillo said if turnout fell in line with electoral commission expectations, traditional maths would suggest that could shave as much as 2 per cent off Labor’s vote on a two-party preferred basis.

With the latest poll reported on from within Labor (but not backed as the most accurate form of research by its campaigners privately) showing a slight swing towards the party and a contest locked at 52 to 48, that could make all the difference.

But Mr Mansillo said that advantage, which stemmed mostly from a tendency among voters who spoke a language other than English to preference Labor, had slowly been breaking down and had become harder to predict.

Ethnic voters have been one of Labor’s core constituencies, breaking its way on a margin of 30 per cent. This has steadily erased to 5 per cent over recent decades and is thought to still be dropping.

But among political professionals on the ground there is a belief a lower-than-usual turnout could be enough to change the election outcome.

“It will tamp down any possibility of a serious Labor swing,” said one Liberal operative, who said it might turn out to be a close election.

Why a by-election had to be called (Alan Tudge left for family reasons but had been linked to a personal scandal) can set the tone for the whole election and whether it has the appeal of a real contest.

“Previously you had a candidate who could not go outside because he was in the Herald-Sun every other day,” said a Labor strategist.

“Now she (Liberal candidate Roshena Campbell) can and remind people to vote Liberal.”

But the Liberals fear it is one last factor from the last federal  poll in May that could swing this contest and not one in their favour.

Round II

About 15 per cent of Aston’s population is Chinese and party strategists say it has been difficult to capture their perspectives in recent polls.

This group of voters deserted the Morrison government as Peter Dutton began to talk in increasingly strident terms about the prospect of war with China near the last poll. Even in its safest seats, Labor saw huge swings towards it from Chinese voters, while they were decisive across Victorian marginals such as Chisholm.

Has that anger dissipated?

“No,” said one MP.

The ALP reckons it was able to get key seats to outperform a state swing in last weekend’s NSW election because voters in electorates such as Ryde were neither returning to the Liberals nor finished lining up to give Mr Dutton a kick in the pants.

Prime Minister Anthony Albanese suggested Mr Dutton was at the centrepiece of the campaign for Aston, whether for his own campaign or to feature in Labor advertising.

“He made appearances on corflutes last Saturday,’’ he said in Parliament

Whether Labor can come within striking distance of a victory not won by a government in a century seems likely to turn entirely on how Aston’s Chinese voters remember the Opposition Leader when they see his face on a corflute. Or how willing they are to forget the things he said last time.