Illustration: Andrew Dyson. On Monday, Abbott suggested that independent schools were badly done by, allowing Julia Gillard to allege he'd be ''Jack the Ripper'' when it came to cutting funding for government schools. The Coalition had to quickly try to clean up its own mess, insisting it wouldn't leave any schools worse off. The political pressure cooker, as the parliamentary term goes into its last year, plus constant media scrutiny in the round-the-clock cycle ensure any error gets maximum airing. Perhaps the surprising thing about Abbott is that he hasn't made more slips. He attempts to be so disciplined he sometimes looks like he's been coated with political formaldehyde. The preoccupation with discipline extends to the Abbott office's control over the frontbench. Some shadow ministers rail about the constraints they are under, with the leader's staff vetting and restricting their media engagements. The fear of veering off message is understandable, but there is a cost, especially when the message is uncompromising, which leads to blatant skewing.

Barrister Julian Burnside picked Abbott up over his dodging when asked on 7.30 why he referred to ''illegal'' arrivals seeking asylum, when in fact these are ''unauthorised'' rather than ''illegal''. Burnside is not a politically neutral observer. But it is fair enough to call out Abbott over being loose with the terminology when the motive is likely to be to inflame the debate. Abbott as a politician is coming across as neither subtle nor supple. This makes it harder for the voters to get a grip on what makes him tick and what he would be like as PM. It also means it is difficult for Abbott to adapt to changing circumstances. If trust is the Prime Minister's stand-out problem, Abbott's is credibility. Put simply, the man exaggerates. Whatever you may think of the carbon tax, for example, it is never going to be responsible for all that Abbott claims. Nor is the government as bad as he says. And Australia's economic situation is better than he allows - although he has recently slightly nuanced his line here, to emphasise how much better things could be under another government. Labor's challenge is to turn Abbott's over-hype back on him. On carbon, it started just before the tax began on July 1, stepping up the effort when that commencement went quietly (although there are more electricity bills to come - the government shouldn't celebrate too early). Craig Emerson's dreadful No Whyalla Wipeout was part of this effort to point to the ludicrousness of some of Abbott's claims. If trust is the Prime Minister's stand-out problem, Abbott's is credibility. Put simply, the man exaggerates.

The as-yet-unanswerable question is whether a discredited government has sufficient firepower to discredit an opponent who is stretching credibility. Cabinet minister Greg Combet, during a ferocious government attack on Abbott in Parliament yesterday, declared hopefully: ''The deceit will go up and up, and it is going to clean out your credibility big time.'' It's difficult for Labor on the carbon tax, because of Abbott's success in demonising it; on the other hand, initial polling showed people's experience hadn't matched their fears. If Abbott insists on simply repeating claims that he can't properly substantiate, this will feed into voters' questions about him. Yet having planted the carbon tax at the centre of his election strategy, and kept the debate black and white, he finds it hard to deal with facts that don't fit the line. Hence his discomfort under Sales' questioning about Olympic Dam, when the comment of BHP Billiton's Marius Kloppers on tax was put to him. Kloppers said the South Australian and federal governments and all the agencies ''that have worked with us to make this a reality have been absolutely wonderful partners to have''. Asked whether the issue of tax had come into the judgment to hold back, he said the decision was almost wholly associated with capital costs - the tax environment for this project hadn't changed (the mining tax doesn't cover the minerals at Olympic). Abbott went to earlier comments from the company about tax. But he came off second best - no wonder he doesn't front up too often on that and similar programs.

Abbott has been extraordinarily successful as an opposition leader. This week, however, brought a sharp reminder of a vulnerability which has previously been a strength - his absolutism. Loading Michelle Grattan is The Age's political editor. Follow the National Times on Twitter