Well, that's that then. After four years of the most bizarre mutual reversal and repositioning imaginable for any policy area, Australia now has a fully-legislated emissions pricing scheme.

And will have, for as long as this government survives, which is not exactly something you would take to the bank.

It's kind of obvious, but it's worth repeating: if Tony Abbott wins the next election and becomes prime minister, his biggest and most urgent tasks will be those of the demolition variety. All that over-developed Abbott musculature, painfully amassed over countless early morning feats of man-craziness, will be required in full for the wrecking job that awaits him at The Lodge.

Scraping back the carbon tax. Prising the permits from the paws of the polluters. Wrenching the seed funding from myriad alternative energy entrepreneurs (a deceptively tricky proposition; just because someone's proposing to generate baseload power from potato peelings doesn't mean they're necessarily going to take dispossession lying down). Digging up the National Broadband Network. The backbreaking grunt work of returning all that money to all those mining companies. Dismantling the Department of Climate Change and Energy Efficiency.

All this before you even consider the work involved in designing stuff to take the place of all this wreckage. Or how to pay for the new stuff (a task even more Herculean than the elimination of existing policies, and one for which shadow treasurer Joe Hockey has rather mercilessly been volunteered).

Don't get me wrong; it's entirely Mr Abbott's right to campaign against anything he pleases, and he is serving an important democratic purpose in doing so. No-one in a democratic system can seriously take issue with the legitimacy of someone who proposes an alternative approach.

But if dismantlement becomes the singular, or even the principal purpose of an incoming government, experience tells us that trouble soon follows. Look at the Gillard Government, haunted by its silent task of erasing certain telltale traces of its immediate predecessor. Any government that defines itself overwhelmingly by what it is not, rather than what it is, creates a hollow at the core of its being, especially once its enemy has been eliminated.

And that is the strange, almost maniacal equation at the core of Australian politics right now: Two protagonists who cannot stop talking about each other. What would Julia Gillard have to talk about if the irresponsible, innumerate wrecker Tony Abbott were not available for constant reference in her press conferences and radio interviews?

And what would Tony Abbott do, if he finally achieved the removal of the lying, feckless woman he identifies as the thorn in the heart of Australia's future prosperity?

Tony Abbott is Julia Gillard's alibi, just as surely as she is his. Without the other, each passionately insists, the path to peace and security would become untroubled. The extent of each leader's determination has, in recent months, become unbelievably clear; Julia Gillard is prepared to allow for the possibility that asylum seekers will die at sea while making a point about Mr Abbott's intransigence, while the Liberal leader happily consigns Australian businesses to further years of uncertainty, just to defeat a model for addressing climate change to which his own side of politics was fully committed just a few short years ago.

When Australia last changed the partisan stripe of its federal government, the demolition work scheduled for its incoming prime minister was comparatively modest; in the main, it consisted of the dismantlement of Work Choices, an industrial regime so comprehensively orphaned by the 2007 election that the Coalition did not even vote to defend its honour.

Imagine if the Rudd Government had come to power promising to abolish the GST, renationalise Telstra and remove private schools funding to boot. That's the scale of the task that confronts Mr Abbott now.

Annabel Crabb is the ABC's chief online political writer.