The political story of the week - which would have got far more attention if it hadn't been for the tragedy in Christchurch - was the parting of ways between Hone Harawira and the Maori Party.

When people are dying on a massive scale, political manoeuvering, quite rightly, is shunted way down the news cycle.

While superficially it's a falling out of individual caucus members in the Maori Party, its ramifications could determine the outcome of the next election.

An agreement was reached on Wednesday between the Maori Party and Harawira to avoid a messy legal and political scrap over his imminent expulsion.

The essence of the deal was that Harawira resigned from the party and will form a new party to contest the next election.

He promised his former caucus colleagues not to stand candidates against them - and they in turn agreed not to run against him in Te Tai Tokerau. They will collaborate together until the election.

A Labour Party strategist lamented to me that now Harawira was gone the Maori Party was in National's pocket forever.

This scenario was echoed by a senior National official, who gloated they had lanced the boil of Harawira and the Maori Party was now their long-term, docile and trouble-free coalition partner.

We should always be careful what we wish for. We just might get it. But it may not be what we thought it was. The expulsion of Harawira may well be John Key's Achilles' heel - one that takes him down in November.

Let me explain. Harawira now has a safe seat and will be returned in November. For the rest of the year he will run a campaign against the seabed and foreshore changes.

But more threatening to the status quo is that he will run parallel campaigns against low wages, so-called welfare reform, mining, GST and privatisation.

These issues will mobilise support among Maori and non-Maori working class.

You can say what you like about Harawira, but no one doubts his sincerity when it comes to fighting for the poor. This is a constituency screaming out for a staunch champion. In Harawira they'll get one. Harawira will target these voters for their party list vote.

The Maori Party, on the other hand, needs to win back its four current electorate seats to be relevant. On current polling, Pita Sharples in Tamaki Makarau and Rahui Katene in Te Tai Tonga are goners and the party won't get any party list seats. The likely outcome is them hanging on to just two seats.

I suspect Harawira's new party will get one to three seats from his party list in addition to his own. As a consequence, even if the Maori Party leadership stuck with National after the election they would be neutralised by Harawira if he got other MPs in with him. Hell would freeze over before Harawira went with National.

But if that's disastrous for National, it gets worse. That's because for Sharples and Katene to keep their seats, they will need Harawira to ask his supporters to vote for them. What's the price of that? The Maori Party endorsing Harawira's party list? Meeting together after election day to agree on a joint negotiation with either National or Labour?

Imagine this scenario: the Maori Party is able to keep its four seats and Harawira picks up 2.5 per cent, as well as his own seat. That makes seven seats in all - two more than they had at the last election.

Given that the Maori seats will overwhelmingly support Labour on the party vote, it's quite possible all seven MPs will back a Labour-led government as part of a joint negotiation strategy.

Taking into account there will be more than 120 seats in the next parliament (in the event that the Maori Party wins more electorate seats than its party vote), the National Party, even with Peter Dunne and Act, will need 47 per cent of the party vote to win a majority. Last election they got 45.

Any takers for John Key sleepwalking to victory now?

Footnote: Matt McCarten was involved in negotiating the settlement in Hone Harawira's departure from the Maori Party.