In the wake of the rise of the Opportunity Party in recent opinion polls there has been much commentary about the role of smaller parties as kingmakers when it comes to forming governments under MMP. Most of it has been overstated.

The folklore is that New Zealand First is the party that usually determines whether National or Labour leads the government. However, in fact, this has been the case in only two of the ten elections held so far under MMP – in 1996 and 2017. In both cases New Zealand First conducted parallel negotiations with both National and Labour before deciding which party to anoint in government.

Labour chose to go with New Zealand First and UnitedFuture in 2005 which kept the Green Party out of office. In 2023 National invited New Zealand First to join it and ACT to get the current coalition over the line.  However, in neither 2005 nor 2023 was the other major party (National in 2005 and Labour in 2023) involved in any post-election government formation negotiations, meaning a kingmaker situation did not apply.

In its day, UnitedFuture was a more persistent player in government than any other smaller party under MMP so far. It was part of successive Labour- and National-led governments formed after the 2002, 2005, 2008, 2011 and 2014 elections, although it was never in the position of determining whether those governments were Labour- or National-led. (In 2005, there had been the brief possibility of UnitedFuture, ACT, the original Māori Party, and potentially New Zealand First joining National to form a government to displace Labour, but such a five-party coalition was too unwieldly a combination to have been seriously considered.)

Apart from 1996 and 2017, it has been clear on election night on each of the eight other elections held so far under MMP who the lead party of government would be. The post-election negotiations therefore have been about the configuration of support party arrangements, and what role, if any at all, smaller parties might play in the government that was being formed.

In 2014, National had an outright majority on election night, so did not need support partners, but decided to keep its existing partners anyway. It quickly signed agreements confirming their support on confidence and supply only and no other policy matters because it felt that was unnecessary, given its apparent majority. But when special votes were counted, National had lost that election night majority, giving its support partners (UnitedFuture, ACT, and the Māori Party) considerably more influence. The looseness of the confidence and supply only agreements National had signed immediately after the election meant that for the entire 2014-2017 Parliament every policy had to be negotiated separately with those support partners.

Although the Opportunity Party's pledge that, should it make it to Parliament and be in a position to determine the shape of the next government, it will begin post-election talks with the largest party first is a noble and sensible position, it may not ultimately be a practical one.

For example, some, but by no means all, recent opinion polls suggest Labour will be the largest party in the next Parliament. On that basis, the Opportunity Party could be expected to begin post-election talks with Labour first. But to form a majority government Labour would also need to involve the Greens and Te Pati Māori. Even then, the polls suggest the margin for such an arrangement would be only a seat or two, which would be very unstable. Compounding this potential mix would be the vastly differing positions of all four parties on tax, making it hard to see how a workable compromise could be achieved between them, especially since Labour has said the only new tax it is prepared to consider is its own capital gains tax.

But if the Opportunity Party decided that was all too difficult and the potential outcome so unworkable, that it would be better talking to National, the position would be no less challenging. For a start, National's leader has so far consistently and arguably unwisely ruled out any negotiations with the Opportunity Party, although his intransigence would surely change if realpolitik dictated otherwise. And then there is the position of New Zealand First and ACT to consider. Neither would be likely to want to concede any ground to the Parliamentary newcomer.

However, based on the experience of eight of the ten previous MMP elections, the Opportunity Party, should it win seats in Parliament, is unlikely to face having to make that choice. Instead, it is far more likely to find itself being asked, if needed,  by one or other major party for support to help make up the numbers to govern, but with no option to go elsewhere.

So, while commentators may like to confer kingmaker status on parties, it has seldom happened in practice over the last thirty years of MMP.  The far more likely prospect remains that rather than shape events as a kingmaker, smaller parties will continue to be invited by one or other of the major parties, and on their terms, to help them form a government.