If voters aren't scared of the negative tactics employed by Malcolm Turnbull and Bill Shorten recently, then they should be. Not because of what the leaders are saying about each other, but of what they are saying about themselves, writes Mungo MacCallum.

So at long last, this weekend, the voters get to choose. Not that it's much of a choice: which putative prime minister do they least distrust?

The last few days of the campaign have degenerated into a screaming match of dodgy scare stories - a barrage of negativity that can only erode what little faith the punters have retained in the political process.

Neither Malcolm Turnbull nor Bill Shorten is believable, and neither will be believed: the absurd demonisation of their respective opponents has gone way over the edge of credibility. But both sides have garnered just enough shreds of truth to make their cases without having been silenced by a thunderbolt from a just deity. So let us try them for size.

Turnbull thunders that Shorten's assertion that the Liberals want to privatise Medicare is the biggest lie of the entire campaign, which is a pretty big call in itself. And indeed, the Liberals have no plans for selling the political icon - at least for the moment. Turnbull has promised, hand on heart, that Medicare will never, ever, be privatised.

It was perhaps not the most fortunate choice of words: about 20 years ago another Liberal prime minister, one John Howard, pledged that there would never, ever, be a GST. But of course what he meant was not yet: as soon as the next election was nailed down and the heat was off, the GST was not just back on the table but was being marketed assiduously and aggressively at public expense.

It is fair to ask whether Turnbull's solemn undertaking would be any more permanent if the opportunity to reverse it arose. So Shorten's so-called scare campaign - just the latest from both sides in this unedifying election - may indeed have some substance. The Libs may not be game to sell off Medicare, but that does not mean that they have to like it - or any other manifestation of publicly funded health policy.

It is easy enough to go back the last three years - Tony Abbott's promises of no cuts to health, education and the ABC, then the attempt to introduce a co-payment (read: charge to patients) for Medicare services, the slicing away of pathology and other areas, the reinstatement of what was supposed to be a temporary freeze on rebates, the so-called reviews of handing over the payment system and maybe other bits of human resources to free enterprise - Turnbull's record of preserving Medicare in all its pristine glory is hardly a convincing one.

But of course the Liberal ideological opposition to public health - indeed to public everything - goes far further back than that. In the early 1930s, the then Country Party leader, Earle Page, was inveighing against the establishment of a public hospital system: it was, he thundered, unfair competition against the private hospitals, of which, by pure coincidence, he owned one.

His crusade continued until Robert Menzies made him health minister in 1949, when he immediately established another nice earner, the private health insurance network. The private funds grew and waxed rich, but then Gough Whitlam proposed the idea of Medibank, the precursor of Medicare.

The conservatives, egged on by the doctors, were outraged: socialised medicine, they screamed and fought the proposals tooth and nail, up till the 1974 joint sitting of parliament that finally and painfully brought Medibank into being.

But not for long: when Malcolm Fraser brought the coalition back into government, one of his first (and one of his only) policies was to cut Medibank down. He reduced it to a shadow until Bob Hawke resurrected it in the 1980s. Since then it has become something of a sacred cow, but this has never stopped the Liberals from undermining it by stealth.

Howard and his health minister Tony Abbott (who boasted that his government was the best friend Medicare ever had) did everything they could to boost the private funds; they saw the private system not as a complement to the public system, but as a fierce and favoured competitor.

And so when Abbott battled his way to the top job, the war of attrition continued.

The problem is that Medicare is undeniably popular; the idea that it could be sold off is politically untenable. Turnbull knows this, hence his overblown protestations. He may even believe them - for the moment. But if history is any guide, the Coalition will eventually strike back.

Shorten's big scare campaign is tenuous, but the same can be said of Turnbull's own tactics. The assault on reforming negative gearing, which Scott Morrison said would throw a sledgehammer (or perhaps a wrecking ball) into the entire economy was only trumped when he and Turnbull warned the world that Shorten had declared war on business. Nonsense, of course; but the fact that Shorten is not enamoured of the big end of town can be documented, and thus the scare could be flimsily justified.

And then there are the ever-reliable boats: Turnbull has implied that Shorten would go back to open borders, that the dreaded people smugglers are ready to unleash their armada, countless numbers would flock to our pristine shores and thousands would drown at sea in the process. In fact, Shorten won the fight at Labor's national conference, and the policy of border protection is essentially unchanged.

But not all of his supporters like it, and of course the Greens don't like it at all. Thus Turnbull said the boats would return as a result of an alliance with Labor, Greens and independents - an alliance that Shorten has constantly rejected but which both major parties vied for after the 2010 election, although we don't talk too much about that.

And Brexit is a real problem for everyone, allowing Turnbull to claim that only the Coalition could avert chaos and poverty through the fragile Australian economy. He offered, he told us, stability. The Liberal Party may be bitterly divided, but it hasn't knocked off a leader for nearly 10 months, so that can be called stability, of a kind. Of course the truth is that there is very little Turnbull or anyone else can do about Brexit, but hey, why waste a good scare campaign, especially at the eve of an election?

It's not all negative. Shorten has his 100 positive policies - although no-one can remember more than about six of them. And Turnbull has his 10-year national economic plan - although he admits it's really only a three year plan.

But as we cut to the chase, both men seem more comfortable slandering their opponents than enthusing the public over their own visions, such as they are. If the voters aren't scared they should be - not because of what the leaders are saying about each other, but of what they are saying about themselves.

Mungo MacCallum is a political journalist and commentator.