All candidates have claimed they will be able to foot it against Mr Key in Parliament and election debates and the Question Time series was designed to let them prove it. None got a real hit in.
However, Mr Key was also unable to get in a real hit in return, partly due to the Speaker reluctantly heading him off at the pass, despite his attempts to point to the jobs creation scheme in Labour from its high leadership attrition rate.
Earlier today, Mr Key accused Mr Cunliffe of lying about whether he would rule out Greens co-leader Russel Norman as finance minister.
Dr Norman has signalled his interest in the role if a Labour-Greens coalition came to power at the next election, but Mr Cunliffe has ruled that out should he become Labour leader.
Mr Key today accused Mr Cunliffe of lying on the issue.
"Go and ask David Cunliffe this question - if in the end he is the leader of the Labour party, and if in the end the price of having a government with the Greens is Russel Norman being deputy prime minister and minister of finance, will he rule that out categorically?''
Mr Key said the answer to that would be no.
When put to him that Mr Cunliffe had ruled it out, Mr Key said: "He's lying to you.''
Mr Key said Mr Cunliffe would "get desperate to become prime minister''.
"In the end he'll do whatever it takes, he might say whatever it takes, and come the moment, if that's the price, he'll say, `Well, I'm doing my bit for the country.'''
Mr Key said he would transparent about who he would work with, saying he had ruled out New Zealand First leader Winston Peters at the last two elections.
"I didn't even have his number to give him a ring.''
Mr Key said he would make it clear to the public if he changed his position on Mr Peters.
"But no one is going to believe David Cunliffe when he gets up there and says he won't be working with Russel Norman - it's just not true.''
Mr Key said both Mr Cunliffe and Dr Norman were "hurtling'' towards the political left, while his Government had put forward moderate, centre-right policies.
He said he really did not care about who led the Labour party.
"They will parade themselves around and it will be all fun and games, but eventually New Zealanders will go to the polls next year and make a choice about which policies are going to take this country forward on the issues that actually matter.''
Earlier, Mr Cunliffe told Radio New Zealand the Labour leadership race against Grant Robertson and Shane Jones would be "really competitive''.
"It's a good thing for the party and I've got two very able colleagues that I'm racing with, and we're going to be working together after the race. But of course the big picture is, who can win the country.''
Mr Cunliffe said support for him and the others was even within caucus - but he was comfortable with his level of support around the party base.
"This is about what is best for the country and best for the party as a whole, it's actually not about the individuals. We're only there to serve the group.''
Asked what he could do that former leader David Shearer could not, Mr Cunliffe said that was for others to judge.
"But the feedback I'm getting is that I'm pretty high energy, I'm willing to lead from the front, call a spade a spade and help the party move forward in debate against John Key's National party.''
Questioned on how the shift to the left would affect middle New Zealand voters, Mr Cunliffe said Labour needed to earn the confidence of the labour movement first.
Mr Cunliffe responded to Mr Key's comments this morning, saying: "Mr Key probably ought not make statements about other people telling lies because his record might not be entirely clean.''
Mr Cunliffe again ruled out appointing Dr Norman as finance minister under a Labour government.
"But I have said that he is an able and senior politician with whom we would have a good relationship and there could be a place for him within our economic team. It would not be as minister of finance.''
