The first hint that an early change could occur at the highest level of government in Australia was detected in the release last week of Rio Tinto’s annual profit.

While investors were focused on the bottom line loss of $US2.99 billion and the generous 15% dividend increase designed to placate angry shareholders, there was a different focus for politicians who discovered for the first time the size of the tax crisis they had created.

The line in the Rio Tinto document which eluded most investors and followers of the mining industry was titled “recognition of deferred tax asset following introduction of MRRT – $1.13 billion”

Decoded from the language of accounting that means Rio Tinto received a tax benefit, not a cost, of more than $1 billion from the Australian government’s Minerals Resource Rent Tax.

Forgive Dryblower for being old-fashioned but he always imagined that tax was a cost, not a benefit.

Not so, it seems, with the appallingly designed “super tax” which has been tearing the Australian government apart for the past three years, first because of the way it was dumped on the mining industry and state governments without consultation and then in the way it was used as an excuse to sack then-prime minister Kevin Rudd and install Julia Gillard as PM.

Today, the winds of change are blowing the other way, with Gillard and her deputy, Treasurer Wayne Swan, feeling a chilly wind down their collars as government members discover that the MRRT is a dog of a tax that is not raising much revenue and, worse still, is responsible for a massive hole in government finances.

There’s not much point (and not enough time or space) for Blower to list the full history of the MRRT which started as the Resource Super Profits Tax but was redesigned by Swan and Gillard with the active assistance of three big miners, BHP Billiton, Rio Tinto and Xstrata.

What Swan and Gillard wanted from negotiations was an end to a damaging anti-tax advertising campaign ahead of a general election.

What the miners wanted was a tax on iron ore and coal that did minimal damage to their balance sheets.

Looked at that way both sides got what they wanted, with the losers being the taxpayers of Australia who were promised much and got nothing.

Well, they actually got less than nothing because Swan and Gillard blundered so badly that they imagined the tax would raise oodles of revenue which they proceeded to spend before the cash was in the till.

Politically the MRRT and its predecessor is shaping as the tax that raised little but successfully ended the careers of many politicians, such is the state of public opinion polls which shows the Gillard government heading for a thrashing in September.

Can a political revival be orchestrated?

That’s what makes this week’s flow of profit results so interesting because over the next few days we will see a string of iron ore miners follow in Rio Tinto’s footsteps, starting tomorrow with Mount Gibson Iron, followed on Wednesday with BHP Billiton and Fortescue Metals Group and finalised on Tuesday next week with Atlas Iron.

As each company reports, there will be close focus on profits (and perhaps some losses), as well as that “tax line” in the accounts which will disclose whether any provision has been made for the MRRT, or whether the companies are to receive a tax benefit.

From a strictly financial perspective the MRRT, payable now or as a deferred tax benefit created by generous depreciation provisions and offsets against state royalties, is the super-tax working as it should, encouraging miners to invest in their operations.

From a political and government finances viewpoint it is a disaster of immense proportions because the revenue receipts forecast by Swan have already been spent on vote-buying social welfare handouts that now have to be funded by increased government debt.

Little wonder that Rudd, the man whose career as PM was cut short by the 2010 tax revolt, has been raising his head above the backbench trenches, scoring points off his political enemies (in his own party) and acting more like a PM-in-waiting than a man defeated.

It is into this toxic brew of backroom dealings over mining, tax and political power that the iron ore miners will march with their latest profit results and revelations about whether they are providing for MRRT, or not.

Shareholders in the companies concerned will be watching closely.

Australian government ministers and backbenchers will be watching even more closely.