When Parliament rises for the year at the end of next week, MPs' attention will shift over the summer break to the election next year, and what it might mean for them personally. Some will decide the time is ripe for them to move on, as did Green MP Jan Logie this week, and announce their retirements early in the year.  

The Prime Minister's focus will shift to the future composition of her Cabinet, with a significant reshuffle already promised for around late January. She will be looking to a team that both maximises the talent in her Caucus and presents a reinvigorated and positive face to voters for what the polls show will be an extremely difficult election contest for Labour. 

Refreshing Cabinets is a challenging task for any Prime Minister. Leaving aside the question of talent, the exercise is always fraught, given the ambitions and personalities involved. Over the years various Prime Ministers have attempted to refresh their Cabinets for election year, but few have done so successfully. 

When he became Prime Minister in early 1972 Jack Marshall took the axe to the long-serving Holyoake Cabinet he inherited, bringing in four new Ministers to replace those who had indicated they would be retiring at that year's election. But that did not stop his government losing to Norman Kirk's Labour Party in a landslide a few months later. 

At the start of 1990, one of Labour’s more dismal years, Prime Minister Geoffrey Palmer moved aside six retiring Ministers and brought in some of Labour's better backbench performers to replace them. Some of the former Ministers remained openly disgruntled about their demotion throughout the next few months until Labour's landslide defeat.  

Following the collapse of the National/New Zealand First coalition government in 1998 Prime Minister Jenny Shipley sought to reshape and refresh her new minority government through one of the boldest pre-election reshuffles of recent times. But despite giving her government a new face, it was ultimately to no avail. Helen Clark and Labour still won the next election by a handy margin. 

Prime Minister John Key took a more cautious approach. While he regularly reshuffled his Cabinet at the start of election year, he never demoted more than one or two Ministers. This both minimised the scope for disgruntlement, and always left the door slightly ajar for the ambitious. 

The common point arising from all these different approaches of the last fifty years or so is that pre-election Cabinet reshuffles have virtually no impact on a government's political fortunes. The record strongly suggests that any Prime Minister who believes a government's flagging political fortunes can be revived by an election year reshuffle is dreaming. 

But that is not to say there is no point in reshuffling the current Cabinet. Some Ministers are clearly overworked, others underutilised, some may have intimated privately to the Prime Minister that they will not be seeking re-election, while others have shown themselves simply not up to the task. For these reasons, a reshuffle makes good sense, but the Prime Minister's task will not be easy. 

While the Labour Caucus normally selects Ministers and the Prime Minister allocates portfolios, there is more scope for a Labour Prime Minister to act unilaterally when it comes to reshuffles. But even so, Jacinda Ardern will not have an entirely free hand, the regard in which she is held by the Caucus notwithstanding. 

For example, there has been much speculation about the futures of Ministers Nanaia Mahuta and Willie Jackson. Mahuta’s credibility has been severely damaged by the Three Waters saga, but her value arises from being Labour’s bridge to Tainui and the Kingitanga. Jackson’s comments on the TVNZ/RNZ merger have been consistently belligerent and aggressive, earning a rebuke from the Prime Minister. 

However, beyond that, and most importantly, both are senior members of Labour’s highly influential Māori Caucus – the so-called First Fifteen – which makes it almost impossible for the Prime Minister to act against them. That adds to her challenges regarding the reshuffle – it will not look like much of a change of guard if a same/old situation remains, for whatever reason. 

Given history’s lesson that election year reshuffles have little actual impact on the political fortunes of the government of the day, the Prime Minister cannot expect her forthcoming reshuffle to deal her an election-winning hand. The best she can hope for is that her reshuffle irons out some of the current workload and performance imbalances and provides some promotion opportunities for some of her newer MPs. At the same time, she will need to be attuned to the feelings of those backbenchers passed over in the reshuffle now having to accept the reality their opportunities to go further have passed by. 

All these factors add to the challenges confronting Jacinda Ardern as she ponders the future shape of her Cabinet. But no matter how the reshuffle is finalised, then presented to the public, it will still be essentially the same government as before. 

And it will still be that government and its performance that voters will judge at election time, no matter who is in the Cabinet at that point.