The new book on the leadership of the National Party, Blue Blood, is like a favourite horror movie: it is still gripping even though you know what the ending is.
It starts with John Key's shock decision to step down as prime minister at the end of 2016, and his succession plan kicking in.
It all went well - until it turned to custard in the midst of a global pandemic and the party is now onto its fourth leader in just over two years.
Succession planning is one of those things that is often talked about in whispered tones within a political party.
It can be forced into the public by events, as evidenced by the failure of James Shaw to get sufficient support at the Green Party AGM for another year.
It will be five years on Monday since Jacinda Ardern became the leader of the Labour Party and internal speculation has already begun about the next Labour leader.
As with Helen Clark and John Key's prime ministerships, there is no suggestion that Ardern will be challenged.
She is still well in front as preferred Prime Minister in all political polls. But with the National and Act bloc roughly level pegging with the Labour-Greens bloc, her chances of leading a third-term Government are no longer overwhelming.
If Ardern loses the next election, however, there will be a leadership contest. And that would most likely be between Chris Hipkins and Michael Wood.
Hipkins is popular with the public and the media and is the Mr-Fix-it in Cabinet. He has taken over the troubled police portfolio, after taking over health and Covid-19 at the height of concern over the pandemic. He is affable and has a good sense of humour.
He is aged 43 and came into Parliament in 2008 as MP for Remutaka after working as a political adviser in the Beehive.
Michael Wood is less experienced but has made an impact in the short time he has been a minister – his nickname in the Beehive is "Napoleon." He is competent, efficient, and firm.
He has been trusted with the Fair Pay Agreements in Workplace Relation, with transport, which got the better of Phil Twyford, and has taken over immigration from Kris Faafoi.
Wood is popular with the party base. He is a former union organiser, has an ability to think on his feet in the House and draw appealing contrasts between Labour and the Opposition. He is aged 42 and replaced Phil Goff as MP for Roskill in the 2016 byelection.
Given the role the party and the unions have in Labour leadership votes, Wood would have the edge over Hipkins.
Who becomes the next Labour leader is, however, dependent on the circumstances.
If there were a sudden and unforeseen vacancy this year, through accident or illness, Deputy Prime Minister Grant Robertson, and Ardern's close partner in politics, would almost certainly become uncontested Labour leader and Prime Minister.
But in the event of an election loss with Ardern at the helm, it would be highly unlikely that Robertson would want to go from Finance Minister for two terms to leader of the Opposition.
It is not impossible, though not likely, that Ardern could do a John Key and step down but it would threaten Labour's chances of securing a third term.
At the time Key left, in 2016, he had reason to be confident that National could possibly secure a fourth term under Bill English. It had not always been so.
Five years into John Key's prime ministership, most close observers would have picked Steven Joyce as the natural successor in the event of an unforeseen vacancy.
But by the time of the actual vacancy, Bill English as deputy leader and Finance Minister, had become the natural successor and was Key's choice.
There was a certain amount of resentment in the National caucus that Key had organised his succession.
Key had told English of his plans a few weeks before but told Steven Joyce only at 9am on the day of the announcement, the Blue Blood book says.
Key talked to author Andrea Vance for the book and told her he felt boxed into a corner.
"'I think Steven would say I tainted the process. One or two people were a bit angry, or disappointed, that I did that. And I get that. The leader is first amongst equals. If you are no longer the leader, you don't have any right to impose that.
"But I didn't have that luxury," he had said.
"If I didn't say, 'I'm supporting Bill,' I was, by definition, not supporting Bill. That's the inference the media would take. After a decade together, with us being hand-in-glove, if I didn't say, 'He's right,' then I'm actually saying 'he's not right.'
"And I believed him to be right."
The succession plan actually worked extremely well. English led the National Party to the 2017 election where it secured 44.4 per cent of the vote.
But the plan did not figure on either Jacinda Ardern taking over the Labour leadership from Andrew Little two months from the election, or New Zealand First choosing Labour and the Greens over National.
The rest was history for Labour but was, for a long time, a horror show for National.