By JOHN ARMSTRONG
Mistake committed, mistake compounded - Teflon Woman comes unstuck.
In the case of the Great Art Swindle, the Prime Minister lost her Midas touch. She broke her golden rule: 'fess up to a mistake, apologise and quickly move the agenda forward.
She 'fessed up, apologised and then tried to spread the blame by smearing other politicians with the same brush. Her apology was immediately devalued.
As so often in politics, it is not the initial indiscretion that does the damage, it is the subsequent mishandling of it.
Memories were rekindled of Jenny Shipley's fluffing over what was said or not said during dinner with Saatchi boss Kevin Roberts, and her later "I made it up" gaffe regarding TVNZ newsreader John Hawkesby's salary.
Helen Clark was pinged on Sunday for passing off a painting she signed and submitted for a charity auction as her own work. That should have been the end of the matter. But the next day - under questioning from journalists - she admitted that a total of six fakes bore her signature.
The following day, under pressure from indignant MPs, she was forced to confess that her repeated assertion that other politicians were guilty of the same behaviour did not actually apply to any existing MP.
And having accused Act MP Rodney Hide of tipping off the media about the painting's authenticity, she then had to accept his word that she was wrong.
The day after that, the Opposition was demanding that Clark resign her arts portfolio on the reasonable grounds that her behaviour had fallen below the standard she expects of her ministers.
The Prime Minister's discomfort was obvious in Parliament on Wednesday afternoon. After an ashen-faced Clark left the chamber following another gruelling question-time, Labour hauled out the heavy artillery for the following free-for-all general debate, deploying Michael Cullen and Trevor Mallard to restore some kind of balance by rubbing National's face in its own poll rating. Normally, one such heavy-hitter would have been deemed sufficient.
Taking other such credibility-eroding episodes into account, there is no question that "Paintergate" - as the affair has inevitably been dubbed - has most damaged the Prime Minister's reputation.
But how damaging is it? Remember her objection to the boarding-house being built around the corner from her Auckland home, the secret payout to John Yelash to settle his libel suit, and her husband's work-related emails being routed through her office?
Those sideshows lie forgotten in the vapour-trail of her soaring popularity, largely because most people judged that they were irrelevant to the main act - her running of the country.
Given that the painting was signed and sold three years ago, the same logic should apply. But this incident cannot be dismissed quite so easily.
The ethics of signing a painting you did not do are so black and white that they cannot be fudged - they are something everyone can instantly grasp. There is zero upside for Clark.
Instead, she is the butt of jokes and comparisons to Idi Amin and Jeffrey Archer.
Clark has confirmed she is capable of the same sleight of hand as any manipulative politician.
But then she has never pretended to be Miss Goody-Two-Shoes. Her tough exterior and ruthless instinct are part of her appeal.
Neither is there anything pompous about this Prime Minister when compared with the demeanour of Shipley and Jim Bolger.
If Clark has fallen off her high horse, the horse was not that high.
Even so, she is the Prime Minister, and the cavalier use of her signature will come as a shock to those who have placed her on a pedestal since she took office.
National has sought to exploit the disappointment of voters who feel let down, particularly as Clark has made a special virtue of rebuilding trust in Government.
Bill English wants voters to think that because she cannot be trusted with a painting, she can no longer be trusted with a Government.
But this ploy falters because he cannot demonstrate a link between a bit of personal naughtiness and any aspect of Government policy.
English is on more solid ground in arguing that Clark's integrity is far more compromised by Jim Anderton's refusal to abide by the spirit of the anti-party-hopping law, given her fierce denunciation of waka-jumpers before the last election.
But outside Parliament there is indifference rather than anger towards Anderton.
He has jumped wakas. Unlike Alamein Kopu, he hasn't jumped sides and is continuing to support the Government - a Government enjoying extraordinary popularity.
In contrast, Shipley's dinner-party stumble came against the backdrop of public anger over golden handshakes paid to Tourism Board members.
And the Hawkesby gaffe was made in a subsequent television interview when she was trying to rebuild her credibility.
Above all, Shipley was fighting against a strong current of disenchantment with National and a decade-and-a-half of free-market reforms.
Shipley could not afford to make a single mistake; Clark has quite a lot of latitude.
Clark was also lucky the painting popped up in a week when the media were almost exclusively focused on kidnapping and murder.
Another unwritten rule of politics states that luck goes your way when things are already going in your favour.
What the signature saga has done is puncture the aura of invincibility surrounding Clark.
The affair has been an awful comedown after the giddy heights of Washington.
In Parliament, it has seen English outwit Clark for the first time since becoming Opposition leader, giving him a huge election-year confidence booster and something of real nuisance value.
Through the year and into the election campaign, every Government policy position will prompt the following rejoinder from National: is it as genuine as a painting signed by Helen Clark?
By JOHN ARMSTRONG