Ivy League intellect had deterred some people, but would serve him well in his bid to topple popular PM.
The new Labour Party leader is an ambitious, highly educated son of an Anglican vicar whose lofty goals and ego are seen as both an asset and a stumbling block.
After David Cunliffe's election as leader yesterday, former colleagues said that the New Lynn MP had been focused on the top spot for a very long time.
Former Labour Party president Mike Williams, who has known Mr Cunliffe since 1999, said: "I think that's what people hold against him, his ambition. But really, that's what you want - a Labour Party leader and a Prime Minister - because it's exceptionally hard work."
Mr Williams said Mr Cunliffe's Ivy League intellect had deterred some people, but it would serve him well in his bid to topple a highly popular Prime Minister.
"He's got a very good head for figures which probably means he is a match for John Key."
Mr Williams said he had never seen any of the "arrogance and high-handedness" which Mr Cunliffe was accused of.
Former colleagues have also told the Herald that he was warm and caring and never lost his temper under pressure.
Mr Cunliffe, 50, was seen as one of a new wave of Labour MPs who are wealthy, highly educated and comfortable with business groups as well as unions.
He repeated his promise to tax the wealthy in his first speech as Labour leader.
Mr Cunliffe entered Parliament in the Titirangi electorate seat in 1999, and was a successful minister in Helen Clark's Government, in which he held the health and IT portfolios.
After Labour was defeated in 2008, he rose to number three on the party list and was appointed finance spokesman.
When Phil Goff stood down as leader after defeat in the 2011 general election, Mr Cunliffe ran for the leadership but lost to Mr Shearer.
He was demoted to the backbenches in February after he refused to rule out a challenge for Mr Shearer's position at Labour's annual conference in November.
After Mr Shearer resigned on August 22, Mr Cunliffe made his second bid for the leadership.
He now lives in the wealthy Auckland suburb of Herne Bay - outside of his New Lynn electorate. He grew up in Te Kuiti and Pleasant Point, near Timaru.
Mr Cunliffe studied politics at Otago University, where he met his wife Karen Price, an environmental lawyer, with whom he has two sons.
* Born in Te Aroha, Waikato, the son of an Anglican vicar and a nurse
* Educated at Otago (political studies) and Harvard (public administration)
* Worked as diplomat and business strategist
* MP since 1999 for Titirangi and New Lynn
* Former Minister of Health and IT and Communications.