Ardern's challenging last full week as PM

Power Play - Today is Jacinda Ardern's official due date, but for now she remains as Prime Minister.

In response to intense media interest, political staff are trying to plan for an event everyone knows is impossible to predict - the time and exact circumstances of the birth of a child.

Ms Ardern will stay in Auckland, not wanting to "tempt fate" by flying back and forth to the capital. However, she will not formally hand over to her deputy and New Zealand First leader Winston Peters until she arrives at Auckland Hospital.

So there may be a "hybrid" handover period until the baby is born - Ms Ardern will retain the authority and position of PM, but Mr Peters will carry out her regular parliamentary and media commitments, including chairing Cabinet tomorrow.

As she prepares to ease into another role however, her last full week as PM was not without its challenges.

Last weekend came the announcement that Mr Peters was taking legal action against some of the country's most senior public servants, the Attorney-General and former National Party ministers.

Mr Peters views this as an action of a private citizen after details about his superannuation payment were leaked during last year's election campaign, but the possibility he'll have to excuse himself from Cabinet if the matter comes up shows the difficulties of trying to separate the personal from the political.

That's aside from just the look of having the man about to take over as Prime Minister launching such a sensational and politically sensitive law suit against senior government and opposition figures.

Then on Monday came the news that Justice Minister Andrew Little had been forced to dump a repeal of the three strikes sentencing law, one he describes as "the high water mark of policy stupidity".

The theories were flying about the machinations that led to that backdown - a public demonstration of the difficulties of coalition government.

From the start, the three government parties saw the merit in thrashing out difficult issues in private before any disagreements spilled out publicly, so they could present potentially a compromised policy, but one which would have the numbers. That clearly did not happen this time.

Parliament was abuzz with speculation about whether New Zealand First had shafted the Justice Minister, or whether he had misunderstood the party's support for broader criminal reforms as including the three strikes repeal.

Whatever happened, it was an untidy start to a week where there was such a strong focus on the justice system, and one where there should be no questions about the quality of the decision-making process or the mana of the minister. First, there was the three strikes controversy; the week would end with a new style of prison unveiled, and a fundamental debate about how New Zealand should run its courts and prison systems.

Then the bomb that is Shane Jones dropped.

The Labour-turned-New Zealand First MP often skates closer to the line than many MPs would dare, relying on his eloquence and wit to see him through.

He is now playing the line between whipping up grass roots support with his extraordinary attack against Fonterra, against being a constructive minister who makes the PM look good.

Ms Ardern had already reprimanded the Regional Economic Development Minister for his attacks on the partially government owned national carrier Air New Zealand, including a call for the chief executive to be sacked.

Comments Mr Jones made to farmers at Fieldays agricultural event a few days ago leaked out, and he let loose when asked about what he'd said by reporters back at Parliament.

What followed was a full-frontal attack on Fonterra and its chairman John Wilson; fully backed by party leader and Deputy Prime Minister Winston Peters. Fonterra refused to comment or respond throughout.

The problem was Mr Jones had already been told by the Prime Minister to temper his language when talking about New Zealand businesses like Air New Zealand and Fonterra.

She is acutely aware of the "elephant in the room" - business confidence stubbornly low, despite the efforts of Ms Ardern and Finance Minister Grant Robertson.

But New Zealand First has clearly decided tapping into discontent about corporate mismanagement and people in the regions being disadvantaged is as important.

The result was Ms Ardern faced questions throughout the week about the strength of the relationship between the two parties at such a critical time. She has resorted to arguing "personal capacity" in the case of both Mr Peters' legal action and Mr Jones' latest comments.

It's a difficult argument to sustain given Mr Peters' significant political role both before and after the birth of Ms Ardern's child, and when Mr Jones was happy to trumpet his views when addressing Parliament as a government minister.

However with neither Ms Ardern nor Mr Peters inclined to discipline or even criticise Mr Jones he is free to carry on speaking as he wishes.

For now though, the due date - like for any other family - may come and go, while the machinery of government rumbles on.