Why does the Prime Minister not simply sack John Banks? If Banks then left Parliament, National would win a byelection in Epsom and the Government's majority would not suffer for the remainder of this term.
Possibly John Key is looking ahead to his need for coalition partners in a third term but it is hard to see Banks or his party surviving the next election.
In the meantime, Key is beginning to suffer more than his errant partner, particularly under the questions Opposition parties put to him in Parliament this week. Confronted with the findings of the police investigation, Key could only say he had not read the police report.
He could have read it, should have read it. The fact that he does not dare to read it does not say much for his confidence in the former mayor of Auckland who is now a minister in his Government.
The conclusions of the police investigation, which the Prime Minister has seen, were bad enough.
Police found that although Banks had filed a false declaration of donations to his last mayoral election campaign, he had not done so deliberately because he had signed the declaration without reading it.
The contents of the police report, obtained by the Herald under the Official Information Act, are even worse. They show a large number of "anonymous" donations of the same amount - 11 of $5000, 11 of 19,000, three of $20,000, five of 25,000 and a few large donations of other amounts, suggesting the internet billionaire Kim Dotcom was not the only donor who was advised to divide his contribution into stated amounts so that the mayor could claim not to know the donor of each one.
Dotcom told police the mayor said, "I want to help you Kim, and I can help you more effectively if no one knows about this donation".
There is much more in the police report, including from Banks' campaign treasurer about how rich-listers were targeted for $25,000 donations, but the Prime Minister does not want to read it. Banks' failure to read his campaign declaration proved fortuitous, perhaps it is safe policy. See no evil, hear no evil ... and try not to look like a monkey.
Key is not the first prime minister in the modern era to be embarrassed by a coalition partner. Helen Clark had to tolerate similar nonsense from Winston Peters, also over a hidden campaign contribution. Both leaders had sacked or suspended ministers of their own party for less.
Coalition partners probably should be independent to this degree. Let each party answer for the performance of its own. Banks would be feeling some heat from within the Act Party by now if Act had any future. But Banks is where he is because Act needed him more than he needed a second life in Parliament.
He cannot be enjoying it. The Dotcom disclosures have reduced him to a startled rabbit forever filmed evading questions he cannot answer over donations he pretended not to remember. His previous life as a National Minister of Police, a forthright upholder of law and order and lofty values, must seem a long time ago.
New Zealand politics lacks a tradition of dignified resignation. When improper conduct is exposed, the culprit usually clings to office until forced by his or her leader to do the decent thing.
Banks has no leader with that power over him. If Key sacked him from the ministry, Banks could switch his vote to the Opposition, which would change the balance in Parliament. National would rely on the Maori Party for a majority. This seems the most likely answer to the question posed at the outset, why does Key not simply sack him? In the end it is up to Banks. He would do himself and the country a favour if he resigned now.