It should not have taken the discovery of that second letter, relating to the battle Nick Smith's long-time friend Bronwyn Pullar was having with ACC, to justify his resignation.
OPINION: Of course it rubbed salt into the open wound that junior MP Nikki Kaye, and then former associate ACC minister Pansy Wong - the last minister to go from the Key Cabinet under a cloud - managed their conflicts of interest well by referring on a letter from Pullar, ultimately to Smith.
He then, in a clear lapse of judgment, signed out that letter without acknowledging he too had a conflict of interest.
Yet the second letter was more a useful excuse than a final coffin- nail.
From the moment his reference for Pullar came to light, the end was always in sight.
Various attempts to reduce the significance of the letter were made; that it was for a friend, that he made his conflict of interest clear, that he said he was not trying to influence the claims process and that it was only for a medical reassessment.
The fact is, it was addressed "to whom it may concern" so was open to Pullar to use as she saw fit.
Indeed, ACC confirmed that the letter was sent straight to them. It was from ACC files, not from a medical assessor, that Smith retrieved a copy confirming he had sent it on ministerial letterhead.
Her ability to work before her accident was clearly a key element in her claim, as ACC saw it. That was the very issue Smith addressed. So if his reference was used to promote her argument, there was an obvious inference he was trying to influence a decision within his own portfolio.
And it is difficult to see what Smith's reference would achieve, other than to flex political muscle and indicate she had friends in high places. He has a doctorate, but is not a medical doctor. And his view of her abilities before her accident would have otherwise had no more weight than a letter from a close friend of Pullar.
A letter from a qualified medical professional would have been far more to the point.
It is simply gob-smacking that Smith would let his guard down and provide the reference after so staunchly and correctly refusing to intercede on her behalf before.
But that is not the end of the possible ramifications of his error.
From that moment, it was known within ACC that she was a friend of the minister.
However professional ACC staff were, it would have been at the back of their minds when dealing with her.
Only a full inquiry will reveal whether that was an element in the meeting Pullar and her supporter and former National president Michelle Boag arranged with two senior managers at ACC in December - far more senior face- time than most claimants could hope to see.
An inquiry could also clear up whether that knowledge came into play during and after the meeting. ACC has claimed Pullar used the leaked list of names as a bargaining chip to secure a benefit - something she and Boag have vehemently denied.
Yet ACC waited till the leak of names to Pullar was made public by Fairfax Media before it referred the matter to police.
Green MP Kevin Hague is right; there is no way an inquiry by Privacy Commissioner Marie Shroff will clear up those issues.
For now, Prime Minister John Key is resisting the call for another inquiry, but, like the Smith resignation, it has an inevitability about it.
Smith has had a chequered political career, including a conviction for contempt of court, and history may not judge him well.
But he was also one of the most intelligent ministers in recent National governments, able to master complex issues and explain them - and sell them - well. He was also one of the most accessible and accountable ministers, rarely, if ever, ducking the media or interviews.
In my dealings with him I cannot remember a single instance where he has hidden behind a press secretary or failed to return a call.
He was also one of a handful of ministers who understood and accepted without equivocation from early days the science of human-induced climate change.
Having said that, he did over- egg the problems faced by ACC when he took over as minister. It was good politics to claim the previous government had left a ticking fiscal time bomb, but recent cuts to levies - again cleverly claimed as a victory by Smith - showed the crisis was nowhere as deep as he painted them.
There is also a growing sense in recent days that the reforms he led to local government would not be as sweeping as the tough talking suggested.
If the legal test will ultimately be "the public good", it leaves a huge door open for councils to do most of what they are doing now, albeit under a tighter fiscal rein.
But that is not Smith's problem now.
- The Press