National Party leaderhip contender Judith Collins has rejected a suggestion from investigative journalist Nicky Hager that she would be a risky choice for Prime Minister.
Ms Collins, Deputy Prime Minister Bill English and Health Minister Jonathan Coleman have all put themselves forward for the party's leadership, after Mr Key announced his resignation on Monday.
Mr Hager said it would be risky for National to appoint Ms Collins as leader a year before an election, and that communication between her and right-wing attack blogger Cameron Slater, revealed in the book Dirty Politics last year, were damaging.
"Most of it was very petty - nasty little conversations about who they hated and making up little petty names about her political colleagues in Parliament - but sometimes it was actually much more unpleasant than that."
But Ms Collins said Mr Hager was going down his usual track and dredging up innuendo.
She did not think her campaign would be dogged by allegations in Mr Hager's book Dirty Politics, released during the 2014 election campaign.
"I listen to him and I think, every time there's somebody trying to do their best, he's after them. Whether it's John Key, me or Helen Clark."
Ms Collins said the Chisholm inquiry, which looked into an alleged smear campaign against the former Serious Fraud Office director, has cleared her of any wrongdoing.
The inquiry looked at whether Ms Collins provided information about the then-director to blogger Cameron Slater.
She said her emails, text messages and phone calls over six years were gone through for the Chisholm inquiry which had cleared her. There were not hundreds of emails exchanged between her and Cameron Slater, as claimed, but about 10 or 12, mostly sending through stories and press releases, she said.
"This is all about 2017 and who has the ability to lead National into that election and to come out the other side best."
She had support from "quite a few" MPs but was not saying who or how many. "It's much better if we wait until Monday."
Ms Collins said an early election did not necessarily need to be called following a change of leadership.
Former National Party president Michelle Boag told Morning Report she backed Mr English. She said he was policy architect of the government, and had driven public sector reform and a social investment approach to welfare.
"He has been very innovative in policy terms, and I think that the National Party is going to be well served with that continuation of a very popular policy agenda."