Day after day, week after week, month after month, Tony Abbott's opening words in parliamentary question time were almost always the same. It was almost invariably a question to put Julia Gillard on the spot on the carbon tax.

"Will the Prime Minister apologise to the people," it would typically run, "for jeopardising investment and jobs by breaking her solemn pledge that there will be no carbon tax under the government she leads?" Or a variation on the theme.

It was usually delivered with a triumphal air. And it was usually just the first of many opposition questions on the matter for the day. In June, in the run-up to the advent of the tax on July 1, the opposition devoted an average of six questions a day to the subject.

That's six out of eight or nine opposition questions in a typical question time. It was not a monomaniacal fixation, but it was as close as it gets.

When Parliament resumed in August after the winter recess, the opposition kept up the attack, but its enthusiasm seemed to wane. The daily average number of questions fell to four.

Then, on the last sitting day of August, something changed. Abbott's first question to Gillard was about mining and he didn't trouble her about the C word all day. That was August 22.

He hasn't asked her about it since. True, he hasn't had many opportunities. After her father's death, Gillard took leave from Parliament. But even when Abbott had the chance again on Wednesday, he didn't take it. He asked her about the budget.

And the Coalition as a whole asked the government an average of just one question a day about it in September.

What's happened? It's very clear. The carbon tax has been in place for nearly three months now, and Australians are finding that it's not the fearsome End of Days that the Abbott of Doom had foretold.

Australians lived in fear before the tax arrived - 51 per cent said they expected to be worse off under the tax, and 37 per cent expected to feel no difference, the Herald-Nielsen poll found.

But once it had been in place for a couple of months, there was a clear shift. Forty per cent said they were worse off. A majority, 54 per cent, now found they were unaffected.

That is, the percentage of people who moved from expecting a sting to feeling nothing was 11 per cent. That equates to about 1.5 million voters.

These are the people who are now wondering whatever happened to the terrible consequences Tony Abbott had them fearing.

The percentage of people who said the carbon tax made no difference to them personally has increased by 17. That equates to about 2.4 million voters. This is a big reassessment.

The Minister for Climate Change, Greg Combet, now delivers his rebuttals to Abbott's scare campaign with the same triumphal air that Abbott once carried: "The fact of the matter is that there have been no unimaginable price increases as forecast by the Leader of the Opposition," Combet said in question time on Thursday. "There has been no collapse of whole regions or industries. In fact, today, Arrium Mining announced 100 new jobs in Whyalla, that the Opposition Leader said would be wiped off the map.

"Jobs are growing. The economy is growing. This has been the most mendacious campaign we have seen against an important policy initiative and you are going to be held to account for everything you said."

The carbon tax is still unpopular. It is still a potent symbol in the popular mind of Gillard's untrustworthiness. But the exposure of Abbott's fearmongering is now damaging his credibility.

The reassessment of the carbon tax is now playing out not just in question time but in the broader politics of the nation.

This week's opinion polls confirmed a trend. Labor is reviving. The Coalition is flagging. Gillard's approval rating is improving. And Abbott's approval rating has gone from bad to dire.

"At the current level, Abbott's performance is at the level of the most unpopular opposition leader of the last 40 years," says the Herald's pollster, Nielsen's John Stirton.

The most unpopular of all the 19 opposition leaders of the past four decades was Simon Crean. His net approval rating - the percentage of voters approving of his performance minus those who disapprove - has an average of minus 26 per cent.

And Abbott's? His net approval in this week's Nielsen poll was minus 23. Since the 2010 election he has never been above zero, but this is a new low for him.

The average of his popularity over his entire term as leader isn't as bad. Taking his entire time in the job, his average approval rating is minus 7.4 per cent. That puts him at No.12 on the list of 19 opposition leaders. The troubling fact for the Coalition is that none of the leaders ranked at this level or below have ever made it to the prime ministership. Indeed, some of those who ranked higher on the popularity hit chart didn't make it either.

Of course, Gillard is by no means a popular prime minister. Her approval rating is minus 11 in this week's poll. Of the eight prime ministers of the past four decades, she is ranked No.6 on popularity.

But her trajectory is now upwards and Abbott's is downwards.

How much of this, though, has to do with the carbon tax? Surely other factors have been at work. For instance, there is the publicity surrounding the contested claim that Abbott intimidated a political rival at university by punching the wall on either side of her head. That must have something to do with it, surely?

Labor has been gleefully capitalising, sending its women cabinet ministers out on a roster to talk to the TV cameras about Abbott's "problem with women". The Liberals' Kelly O'Dwyer this week dubbed these Labor women "the handbag hit squad".

Perhaps, but the evidence strongly suggests that the big story of the political fortunes is overwhelmingly about carbon: "I'm always loath to attribute a single cause for movements in the polls," says Stirton, "but in this instance there is a good case to be made that Labor's unpopularity was due to announcing the carbon tax, and it's not stretching it too far to say that [the effect of the implementation of] the carbon tax has something to do with Labor's recovery."

In fact, we are now at a clear crossover point. If you chart Abbott's popularity against Gillard's since the 2010 election, there have been only two crossover points.

Gillard was easily more popular until she announced the carbon tax. At that point, she fell decisively below Abbott. She stayed there until the carbon tax took effect and the real-world reassessment took hold.

Then, last month, the two lines on the chart crossed over again. She became more popular - or, more accurately, less unpopular. That new status was confirmed in this week's poll as her lead over Abbott lengthened.

Abbott made two mistakes. First, he adopted a short-term tactic for a long-term contest. Calculating that a minority government was inherently fragile, he ran a ramming strategy at Gillard. Hit her hard enough, often enough, on her weakest point, and the government would fall in six months to a year.

If this had been right, Abbott's exaggerations and fearmongering never would have been exposed. But the government lasted long enough to implement the tax. For Abbott's credibility, this has proved too long.

Second, Abbott's calculation of a quick-collapsing government led him to think that a negative approach was enough. Intellectually, Abbott and his team recognised that they needed to offer the people a positive vision under an Abbott government. But they never managed to deliver it.

So by running so hard, and so angrily, and so single-mindedly on an attack mission, Abbott made himself unpopular and had nothing to fall back on. In effect, it was an all-or-nothing plan. And it has now gone wrong.

Like a plucky soldier who dashes out of the trenches to attack an enemy machinegun, his furiously determined attack might win him a VC for bravery, but will he survive long enough to enjoy it?

Still, his loyalists see evidence of Abbott maturing in adversity. His environment spokesman, Greg Hunt, uses another military analogy.

Hunt compares Abbott to US special forces: "As US Navy SEALs go through their training, they're put through a series of tests of increasing difficulty. As they pass each level, it's called an evolution. Tony has gone through two important evolutions in the last two weeks."

One was his decision on the supertrawler. By deciding to stand against the government's ban, "Tony didn't hesitate when it was recommended to him that we stand by the principle of not allowing sovereign risk - that underlines our positions on foreign investment, on carbon tax, on the mining tax, and now on fishing.

"He knew we would lose the politics on it, but he stood on the side of good policy over good politics."

Second, says Hunt, was the Cory Bernardi episode, when the Liberal senator suggested that allowing gay marriage could lead to bestiality. "Tony was faced with a potentially difficult issue. It came from someone who has been terribly loyal to Tony. But whereas it took Julia Gillard two years to cut off Craig Thomson, it didn't take Tony two minutes to decide to cut off Cory Bernardi. He took a stand on the values and the good of the team even though it was a personal loss."

Belatedly, the Coalition will work harder to articulate a positive vision for Australia rather than just a negative attack. "This is the next phase," says Hunt, "that he's really only just embarking on, to offer a credible alternative government."

For Abbott, this will be the hardest evolution of all.

Mission Rethink For Abbott