This was going to a comment, but I thought my telling off by Ian Mackay and Richard Aston on my previous post was worth a fuller reply

Two regular Pundit-visitors Ian and Richard have tsked tsked me on my previous post, warning me not to believe the "National spin" and "slogan" around National's large lead over Labour. Their argument is that under MMP a 15 percent gap between the major parties doesn't matter. Here's why they're wrong...

First, I'll challenge them to read the post again because Ian's point that "we are in MMP now. Remember that the minor parties can also make a difference" is (sorry Ian) not a very good one given current political conditions.

First, even under MMP 15 percent between the two major parties is a large gap. No party has had that kind of a lead under MMP and not formed the next government, so for the centre-left to be contenders – and for swing voters to feel turning out and voting for change is worthwhile – it has to be closer. And that goes for making the volunteers work hard and even the MPs to pull their fingers out. It's just psychology.

I mentioned the 'missing million' as well. Labour has some very good analysis of that group going on, but the simple reality is that many stayed away because Labour didn't look like winning. If they are 15 points behind in the campaign, where's the motivation for the unmotivated to vote? While Cunliffe was careful not to say it during the primaries, Robertson and Jones both said publically that Labour would need to hit 40 percent to win this one. I don't think that's right, but 31 percent is no mandate to govern on in this political environment.

But yes, as Ian and Ricahrd say, under MMP such a gap can be filled by others. The Greens have 11 percent and the post repeatedly talks about the two parties as a centre-left bloc. That still leaves them close to five percent short, as I wrote. And, as I wrote, you'd be brave to call the election now.

But most importantly of all, it's because this is MMP and the influence smaller parties have that I'm concluding the gap matters. Primarily – again, as I wrote – it makes it very hard to justify NZF going with Labour-Greens.

You may have read my piece last week, which pointed out that NZF has twice as king-maker gone with the largest party. That shows Peters' unwillingness to get offside with the majority of voters, I think. He talks about a "constitutional convention" that the party with the most votes gets the first shot at forming the government.

When pressed on The Nation a couple of weeks back he said that first shot, importantly, amounts to little more than a phone call. But Peters has not survived so long by chasing windmills. New Zealand voters have the same expectation (biggest parties win) and he will be very aware of that if his party has the balance of power.

For him to break his self-styled "convention" (I'm using italics because there is no convention, just his reading of the popular will), his party needs political cover. That assumes he and his MPs even wants a change and those such as Jim Bolger who say he's a Nat at heart are wrong or that the distrust of John Key in New Zealand First is so strong as to have them backing a new government.

To flesh out what I was getting at in today's earlier piece: New Zealand First needs to be able to convince New Zealanders that change is essential and that the race is close enough to justify that. If National is in the high 40s and Labour 15 points behind, I suspect Peters won't be willing to take that argument to the masses.

As for the Maori Party, Richard, they've made it clear they will go with the winner. They seem to want to be King-followers rather than King-makers.

Put that together and I reach the conclusion that without a smaller gap, the minor parties are unlikely to support a change of government. They're going to have to feel that the groundswell around the country is for something different, and I don't know about you but I don't see the signs of that at the moment.

So my argument back to you fine fellows is to not believe the spin when people say the major parties gap doesn't matter under MMP. It does.