There is nothing ordinary about Boris Johnson, the British foreign secretary who touches down in New Zealand tomorrow.

His style is famous (instead of grooming himself before a press conference, he roughs up his hair to ensure it is sufficiently dishevelled).

So too is his ambition to become Tory leader and Prime Minister.

As a backbencher he was important enough to move the markets with his decision to back Britain's exit from the EU.

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It was a decision that was seen as putting his political ambition ahead of his country's interests.

But his bid to claim the leadership collapsed last year after the Brexit vote, and Theresa May cruised home.

Johnson however will get at least one more opportunity to go for the top after the wounds from May's misjudged snap election eventually claim her.

Johnson's shelf-life is nowhere near extinguished.

The same cannot be said of the current crop of New Zealand party leaders.

Parliament resumes this week for its last sitting before the election campaign.

And the campaign could well be the last for at least three leaders of political parties in New Zealand.

Metiria Turei for starters. If the Greens are not part of the next Government either a coalition partner or in a confidence and supply agreement, there is a good chance that Turei will be replaced at the annual meeting next year by either Julie Anne Genter or Marama Davidson.

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She is unlikely to be challenged because that is not quite the way the Greens do politics.

But she may well come under some pressure to step aside after eight years as co-leader if her extraordinary political gambles of the past fortnight do not pay off.

It is difficult to see how the Greens will benefit from her decision to call Winston Peters racist, to admit to cheating the welfare system, and to demonise those don't see her as a victim.

There is only one party in which this makes Turei a hero and that is among people who already vote Green.

If it has attracted support to the Greens from non-voters, it has probably alienated as many voters whose primary attraction to the Greens was for its environmental credentials.

The fact that social media is still raging about Turei's admission nearly a week after the event suggests she got a lot more than she bargained for.

It has been a damaging decision for several reasons.

It drew attention away from the Greens welfare policy which was radical enough to have generated plenty of debate, given that it would remove obligations and sanctions on beneficiaries.

Much of the negative reaction has been less about the lies she told and more about the sanctimony which has accompanied the admission and her reluctance to make good on the debt to taxpayers.

The damage to the Greens also damages the Labour-Greens block. While it is an independent party, it is closer to Labour than it has been and its poor judgements rub off on the block as whole.

Whether by design or accident, Turei's actions of the past fortnight have also subjugated the environmental arm of the party to the social justice arm.

Julie Anne Genter comes from the environmental arm and Marama Davidson from the social justice. Given what happened in the party's list selection, when members reversed Genter and Davidson's position to elevate Davidson above Genter, the most likely successor to Turei is Davidson.

Prime Minister Bill English may have only weeks to go in his political career if he does lead the next Government in nine weeks.

Steven Joyce, the Finance Minister, would not stick around either if National ends up in Opposition.

Deputy leader Paula Bennett would be best placed to step in as National leader but it might end up being a short-term appointment.

If she could not make the adjustment to Opposition politics - and it is a difficult adjustment for any former minister - a battle royal would engulf National during the next term.

The two who stuck their heads above the wall against English and Bennett last December, Jonathan Coleman and Simon Bridges respectively, would be contenders as would Judith Collins given that her combative nature would be an asset in Opposition.

But it would also be the time for Amy Adams to make her leadership move and a Bridges-Adams or Adams-Bridges combination would likely win the day.

This campaign may well be the first and last of Andrew Little's, Labour's fourth leader since the party was tipped out of office in 2008.

It is, of course, possible Winston Peters could crown him Prime Minister after September 23 if New Zealand First holds the balance of power and gets a good enough deal with Labour.

But if he doesn't, Little is toast. He will not get the benefit of a second term in Opposition such as that currently being given to Australian Labor leader Bill Shorten or that eventually afforded to Helen Clark.

Shorten, like Jeremy Corbyn in Britain, has extended his own shelf-life by making major inroads into the Government's majority.

Despite having done a better job as leader than the previous two, David Cunliffe and David Shearer, Little would be expected to resign and would do so if Labour doesn't make it.

But it would be a mistake for Little to resign from Parliament altogether through sheer disappointment.

The experience Little has picked up in almost three years as leader would be invaluable to the next Labour leader and to his own political career.

That leader would probably be current deputy Jacinda Ardern, with Grant Robertson as her deputy.

That would be a reversal of order to the time he contested the leadership against Little - when he won the caucus and membership support but not the unions.

Robertson is the party's most able politician, as his release of the party's alternative budget showed this week.

But if four white males in a row fail to connect the electorate to Labour, Ardern would be the obvious next choice.

Reluctant as Ardern apparently is to become leader, she would be under pressure to put her party's interests ahead of her own.