Power Play - The resignation of Prime Minister John Key throws next year's election wide open, regardless of who takes over from him as leader.
Throughout the year Mr Key has talked about contesting the 2017 election, but in a wavering voice announced this afternoon he could not in all good conscience commit to seeing out a fourth term.
Under his leadership, the National Party has had consistently high public support and much of that has been because of his own personal brand and popularity with voters.
The real test for National now is whether it will sustain those poll ratings with someone else at the helm.
It does have experienced Cabinet ministers ready to step into Mr Key's shoes, most notably Steven Joyce and Paula Bennett, but there are plenty of others who might try their hand - Simon Bridges, Judith Collins or Amy Adams.
And of course there is Bill English, who has received a strong endorsement from Mr Key.
Many view him as an effective Deputy Prime Minister, Finance Minister and wingman to the more ebullient Mr Key.
Mr English has already had a tilt at the leadership, in 2001, but led the party to a disastrous election defeat in 2002.
He has come some way since then, proving himself to be a loyal and competent member of Mr Key's Cabinet, but will not want to face the ignominy of standing in a contest he could lose.
Mr English will canvas his caucus colleagues to make sure of his support before announcing whether or not he will stand, and he is likely to make his intentions clear in the next 24 hours.
Labour will be rejoicing, as Mr Key's resignation gives it fresh opportunities for election year.
Successive Labour leaders have targeted him, viewing him as the key to National's success, but to no avail.
Many of the biggest controversies in his political career he has brought upon himself, most notably being forced to apologise for repeatedly pulling a waitress' ponytail.
He also campaigned hard for a change of flag, spending more than $20 million on two referendums, which resulted in no change and Mr Key having to accept a rare defeat.
He is known for being a "non-politician", in part for his cavalier approach to some constitutional norms, and his persona as an "ordinary Kiwi bloke".
But part of Mr Key's political skill is his ability to play to the audience; a jokey, blokey style on commercial radio, but with the ability to switch to discussing serious and complex policy.
The first sometimes went too far, with one incident in particular ending up with Mr Key in a cage with a bar of soap in a prison joke gone wrong.
That outraged some who have specific ideas about how a prime minister should behave, but others saw it as Mr Key showing he did not take himself too seriously.
Certainly, there have been few prime ministers so willing to discuss their vasectomy, what they do in the shower and the other personal trivia that have been grist to the mill for reporters' colour pieces for several years.
He has said he is leaving primarily for family reasons, as while they have benefited from his position, they have also had to cope with the downsides.
His departure will inevitably raise questions about whether there is another reason he is leaving so abruptly - that was put to Mr Key directly, but he just repeated that he was no "career politician", and that he and his family had had enough.
His family has very much been in the public eye, but even when their actions have brought criticism of him, he has always maintained that they were their own people and were free to make their own choices.
The only time he was publicly disapproving was over comments his son, Max, yelled out at cyclists from a moving car then posted on social media.
There is a double-edged sword, however: if a politician draws his family into the political sphere and they become part of his public image, family members can be more easily drawn into the political debate.
Now attention will turn to who will take over as leader, and as Prime Minister.
It is a very short timeframe, with a special caucus meeting scheduled for 12 December, which should minimise the damage a long drawn-out contest among its MPs could cause.
But it will be a very different National Party heading into next election, whoever its leader, and one the opposition will already be thinking they have a better of chance of beating.