In government, Cunliffe was one of Clark's standout ministers, succeeding, where others failed, in unbundling Telecom's local loop monopoly, and making bold decisions as health minister. But it was the smoke signals of a leadership coup - "miming his disloyalty", as political columnist Jane Clifton put it - that ended this week with Cunliffe's own blood spilt.
After 12 years in Parliament, he has been stripped of his shadow portfolios and is the Opposition's newest back-bencher. This appears to be the end of Cunliffe's leadership aspirations for now but ambition, ability, party support and trajectory suggest it won't end here for this son of an Anglican preacher and a nurse.
He has been described as the new wave of Labour's Third Way politicians: highly educated, wealthy and perhaps more comfortable in a boardroom than a working men's club. That description may explain both his political success and the strong aversion of a chunk of the Labour caucus dubbed the ABC - Anyone But Cunliffe.
He excelled with women and kids but was not so good with other men, the former staffer says. The member for New Lynn is not one for bar-room chumminess. "Elements of caucus just loathed him and I don't understand why," the source says. "Labour is not that rich with talent that they can't afford to throw away one of their best. The flaw was that he was nakedly ambitious. He wasn't a shrinking violet about that."
There was some suspicion about Cunliffe because of his rarified academic qualifications: first-class honours (BA, politics) and distinction (Diploma in Social Sciences, economics) at Otago and Massey universities, a Master in Public Administration from Harvard, where he was also a Fullbright Scholar and Kennedy Memorial Fellow.
Did his scholarship and ambition grate with a Kiwi sense of egalitarianism, the source wonders, because on policy his old boss was left wing.
Someone who knew Cunliffe when he was a diplomat in the early 1990s told the Herald she had assumed his politics were right wing and was surprised to see him in 1999 wearing a bone carving and greeting people with a cheery "kia ora". The cynic in her wondered whether he had coolly considered his options and judged that after nine years of National governments, Labour was his best bet.
That he represents New Lynn (formerly Titirangi) but lives in Herne Bay, where houses sell for $2 million, provides grist for those who believe they spy a fake.
Early on there was suspicion about his political position because of his business background and education, says Mike Williams, who was party president during the Clark years. But that background was an asset because "the Labour Party did and still does lack people with a business background. He was a shoo-in for Cabinet.
"He was a safe pair of hands. His major achievement was untangling the Telecom shemoozle." says Williams who describes him as a "brave" minister and good organiser who attracted good people.
"He's ambitious and has a very big ego but having a big ego is a prerequisite of being a member of parliament. You have to believe you have something special to offer. So why not?"
But it wasn't Harvard or the Boston Consulting Group (where he worked as an economist and business strategist) listed on his CV that first caught Williams' eye in 1999. "He came to my attention because he had his hair dyed bright red." As the party's campaign manager Williams wondered what he had on his hands in the candidate for Titirangi, until Cunliffe explained he had dyed his Tintin locks for charity.
While he was president, Williams didn't detect a particular ambition in Cunliffe to be Prime Minister and considered him a team player. He's been surprised by Cunliffe's behaviour in recent years. "He has clearly been pushing his own barrow, both under the leadership of Goff and Shearer."
The events of last weekend were "a very unfortunate confluence" of reform of the process by which the party elects its leader and the belief in Cunliffe's camp that under the new democratic system their man had the numbers.
A challenger need gather just 40 per cent of caucus support to trigger a party-wide election in which Cunliffe would have fancied his chances because he was perceived to have won the contest when he and the neophyte Shearer toured the rank and file speaking at meetings just nine months ago.
The reason events went so pear-shaped for him last weekend may be that nine months in politics is a long time. "I think the earth has moved since that time," says Williams. Shearer has established himself as leader among the membership and the icing on cake was his speech to the party conference which Williams rated among the best he'd heard in 30 years and Herald political columnist John Armstrong called "a pearl".
Cunliffe may also have miscalculated the strength of an innate desire for unity. "Whatever else goes on in a party," says Williams, "they know damn well that if a party falls apart they can't get elected."
"Look, he's a nice bloke, I like the guy. He was a competent minister [and] in my view he was a team player. I'd have to say that he polarises people. I don't know what it is about his personality but he has the ability to make people utterly despise him."
Two sources who have worked closely with Cunliffe are adamant he is made of the right stuff. The former staffer rates him as an exceptional boss, "warm, friendly, polite, and caring about his staff". The staffer did no see him lose his temper with anyone despite long hours and the pressure of making tough political decisions such as approving animal organ transplants, sacking a hospital board, and going against the wishes of the strong herceptin lobby.
He can't understand why Cunliffe attracts such passionate opposition among his caucus colleagues.
"He had a terrible personality clash with Clayton Cosgrove [a Shearer loyalist]. It is like there are two Cunliffes. The Cunliffe who was cabinet minister dealing with stakeholders was liked and admired."
Quite right, says a health sector source who worked closely with Cunliffe. He is the right type to lead New Zealand, she told the Herald , having character, brains, heart and being in "politics for all the right reasons".
Suggestions of arrogance were "a myth. It's jealousy and spite. He's talented, he's open about his ambitions. That's him he's honest to a fault. He cares passionately about New Zealand and he has ideas about how to make it a better society."
Hence his political ambition a career she said he'd always wanted.
Cunliffe, 48, describes his back-story as that of a lower middle-class kid who rose courtesy of a quality state education. He met his wife Karen, a lawyer, at Otago University and they have two sons.
Cunliffe was born in Te Aroha; his family moved to Te Kuiti and to Pleasant Point, near Timaru, where Reverend Bill Cunliffe became active in the Labour Party.
A source who knows the family, suggests that came of a career working with the poorer sector and rubbed off on Cunliffe junior, who he described as sincere and proactive.
That source believes the politician is the victim of tall poppy syndrome, though he says "there is probably a volume dial that could have been turned down in terms of his own sense of his ability".
The next chance for Cunliffe to push his barrow is February when caucus will be asked to endorse Shearer. Cunliffe has not ruled out a challenge.
Williams counsels against it. "My belief is that if judgment doesn't fail him he will not contest the leadership in February."
Cunliffe's chance will come if Labour loses the 2014 general election, says Williams.
"He has two years not to be seen to be destabilising the party. That's why I think that any rumblings of a challenge in February would be extremely unwise for David Cunliffe."
Time will tell whether that is too long to wait for an unusual talent who is already in his fourth term in Parliament.
