John Key has decided not to share the stage with the leaders of smaller parties in this year's election debates. He said most people would vote for National or Labour and it made sense for viewers to get the chance to consider their potential prime ministers.
But MMP-style government is about more than that. Every election under this electoral system has led to subsequent talks with potential coalition partners. For that reason, voters should have at least one opportunity to see how the potential prime ministers interact with the leaders of minor parties in a debate.
The desirability of this was disregarded for the first time during the last election campaign when Helen Clark and Mr Key told Television New Zealand and TV3 that they would do only head-to-head debates. The minnows were left to their own debates, which, understandably enough, struggled to garner interest.
The more presidential approach may have produced a higher-quality debate in the case of the National and Labour leaders. Both had more time to explain and question policies than would have been the case if a plethora of small-party leaders had also been demanding time in the spotlight.
Yet this format also precluded the sort of impact United Future leader Peter Dunne made in a televised debate in 2002, which featured an electronic worm instantly polling viewer reaction. Viewers were so captured by what they regarded as common-sense comments from Mr Dunne that he easily eclipsed Helen Clark and the National Party's leader, Bill English.
Deprived of such an opportunity this year, the small parties will struggle to make an impact before polling day. In 2008, their only recourse was to begin their campaigns before the major parties. The national focus on the Rugby World Cup makes even that less tenable this year.
It is always tempting for politicians riding high in the polls to decide they will engage with the electorate on their own terms. Photo opportunities and the like may seem a viable and more comfortable alternative to participating in debates.
Currently, John Key has such a temptation. He has restricted himself to two debates on TV One with Mr Goff, another with TV3 and one with The Press newspaper. Other debating opportunities have been summarily turned down.
In matters such as this, the Prime Minister should tread warily. Any tendency to disengage, through an attitude that poll superiority renders interaction with media and voters redundant, invariably comes back to hurt politicians. Even the most fervent party supporters rarely like their votes to be taken for granted.
Another motivating factor for the Prime Minister might be a reluctance to appear in debates with National's erstwhile leader Don Brash. There would be nothing to gain from statements of support from the Act Party leader or allegations of faint-hearted Government policies.
None of the other small parties offer quite that threat, but their polling failures have made it easier for Mr Key and Mr Goff to exclude them from debates without being accused of seeking to minimise third-party influence. If a couple of the minnows had attracted something like 10 per cent of the vote, as seemed the prospect when MMP was introduced, it would have been impossible to treat them so blithely.
Mr Key suggests that "four debates will be enough for people to get a sense of who they want to choose to be the next prime minister". Undeniably, his appearances with Mr Goff will be highly important. But they are not all that matter.
New Zealand's electoral system means the two leaders have a public duty to debate issues with the small parties, parties that they will probably coalesce with for governing, at least once. It may not be in their interests but it is in the interests of democracy.