This has long been a factor encouraging both sides away from extremes of left or right and towards the more moderate, "sensible centre". They've retained only enough pro-business or pro-worker positions to keep their voting, donating and polling-booth-staffing "base" motivated, as well as to provide some product differentiation. The standard approach of recent decades has been for each side to seek to neutralise those issues where the other side is perceived by voters to have the advantage, by saying "me too", while trying to highlight those issues where it has the perceived advantage over its opponents. Polling released last week by Essential, shows the Liberals' great perceived strengths are national security and terrorism, and management of the economy, whereas Labor's strengths are (in ascending order) education, health, housing affordability, the environment, industrial relations and climate change. Note that almost all the contentious issues are economic, broadly defined. Voters see little to distinguish the two sides on population growth and asylum seekers. The government's already pushing hard on national security and terrorism, but Labor will run from any argument over these issues, where it starts well behind in voters' estimations. Of late, however, the parties have departed from the standard script. Realising he lacked the charisma to get away with mimicking Tony Abbott's virtuoso performance of total negativity against the death-wish Rudd-Gillard-Rudd Labor, Bill Shorten thought he had little to lose by abandoning the small-target strategy of most oppositions, and went to the 2016 election with some relatively daring proposals on tax increases, particularly on restricting negative gearing and the capital gains tax discount.

Despite the conventional wisdom that touching negative gearing would be political suicide, Shorten's bravery was rewarded. Now look at the speeches Shorten and Malcolm Turnbull gave last week, and you see both sides planning to widen, rather than narrow, the policy distance between them. Abbott was someone with conservative social values and hard-right economic views that fitted well with a party base that's be drifting to the right for many years. But he knew better than to highlight such views when seeking enough middle-ground votes to win the 2013 election. Which leaves Turnbull with a big problem. His oft-stated position as a small-l liberal means much of his parliamentary party neither likes nor trusts him. To keep them behind him, he's had to loudly espouse policy positions – on big business tax cuts, weekend penalty rates and saving coal mines, for instance – that are far to the right of majority, middle-ground opinion. The further Turnbull's party base has forced him away from the centre, the more Shorten has been emboldened to move his own policies further leftward from the centre than his predecessors would ever have dared. It's clear Turnbull will go to the election offering no real plan to achieve Australia's Paris climate change commitments and making no more than sympathetic noises about the supposedly soaring cost of living, while claiming that big business tax cuts would trickle down and allow big pay rises.

In the meantime, the ever-continuing budget deficit won't stop the government also promising a tax cut for ordinary workers. In echoes of Labor's winning policies at the 2007 election, Shorten will promise concrete action on climate change and on winding back the parts of Work Choices' attack on collective bargaining that Kevin Rudd and Julia Gillard weren't game to. A rhetorical challenge for Shorten will be to shift the punters from their misconceived concern with the soaring cost of living, to the real problem: weak wage growth. Despite that weak growth, I doubt many voters will be greatly tempted by the promise of modest tax cuts. A test of Shorten's leadership credentials will whether he has the courage to avoid matching Turnbull's promise. But with Turnbull sticking to his plan for big-business tax cuts, and his resistance to reform of negative gearing and wage-fixing, this election may well determine the fate of the era of bizonomics.