Forget any distinction between resigning and being sacked. Had Nick Smith not fallen on his sword yesterday, one would have fallen on him fairly promptly.
He had to go. He had to go because he has been silly or misguided or both in ignoring conflict-of-interest rules that apply to Cabinet ministers.
But he also had to go because John Key desperately needed to bring some closure to this unseemly episode with its cast of high-profile National Party figures and explosive allegations.
The public may not know every last detail of the saga. But they will have seen enough for Winston Peters' categorisation of the goings-on as National Party "cronyism and sleaze" to start to find a ready audience.
Such foot-in-mouth follies erode public confidence in a government. Mr Key's and National's poll ratings are not so crash-hot that they give him and his colleagues unlimited latitude.
Dr Smith also had to go because the Prime Minister initially valued loyalty ahead of precaution. Mr Key mishandled things on Tuesday in letting Dr Smith continue in his Cabinet roles after publication of the reference Dr Smith wrote as ACC minister for his friend, National Party activist Bronwyn Pullar.
Mr Key would have been better to have stood Dr Smith down temporarily until he could be sure nothing else was going to emerge to embarrass him, Dr Smith and the party.
So it was salutary and handy that a trawl of ACC files on Dr Smith's instruction should yesterday uncover a further letter confirming his conflict of interest-loaded intervention.
The letter effectively crucified Dr Smith because it reveals he asked ACC provide him with information relating to Ms Pullar's claim.
Such a request, in alerting ACC staff to the minister's interest in the case, might not have influenced how they handled it. But the perception that it might had Dr Smith in clear breach of conflict of interest guidelines in the Cabinet Manual.
Mr Key simply declared that two letters was one letter too many. The day before, he had taken a rather relaxed view as to whether Dr Smith's reference breached conflict-of-interest guidelines. Yesterday, they took on a sudden new importance. Dr Smith's departure will effectively allow Mr Key to shut the door on any inquiry into Dr Smith's behaviour which might embarrass National. But his exit leaves Mr Key far from unblemished.
- John Armstong is The New Zealand Herald's political correspondent.