UPDATED 6.06pm Bill English has confirmed he will run as National Party leader to replace John Key - a contest that will pit him against Health Minister Jonathan Coleman.
LISTEN ABOVE: Deputy Prime Minister Bill English spoke with Larry Williams
English said the caucus knew him well but that did not mean he would win.
"You can't take these things for granted."
He did not nominate a possible deputy, saying that would depend on internal discussion.
He would not rule out standing on a ticket.
He said two thirds of the caucus had never gone through a leadership change before and would want time to consider the options.
English said such contests could divide caucus but the party was aware of the dangers of that and a robust process was in place.
If he wins it will be English's second tilt as leader after he took National to a historic low in 2002. He said he had learned a lot since then.
"You learn more from losing than winning."
Asked if he would offer something different from John Key, he referred to planning rules.
"There some areas I can see there are some opportunities."
He would not say if he would revise Key's promise not to change superannuation thresholds, saying Key had earned the trust of voters by sticking to that.
However he had not had any discussions about it himself.
English said his focus was on the stability of the Government and economy.
Coleman and English both confirmed candidates for Nat's leadership. Coleman promoting himself as the change candidate— Felix Marwick (@felixmarwick) December 5, 2016
Health Minister Jonathan Coleman has thrown his hat as National leader saying there was a "significant appetite" in National's caucus for "a change from the status quo."
Coleman said he could offer generational change and it was clear there was an desire for a contest over the leadership rather than simply rolling it over to deputy leader Bill English.
He said after National's caucus meeting and sounding his colleagues out last night he had decided to run in the vote which will be held next Monday. He had told English before the caucus meeting this morning.
"We need to do what's best for the country as a while and after taking those soundings, and it's a job I've been thinking about for a long, long time, I am seeking the party leadership."
"Everyone in caucus has a vote but I've done some soundings and there is significant appetite there for regeneration and renewal."
Corrections Minister Judith Collins has hinted she will make an announcement about whether she will run for the Prime Minister's job this afternoon.
Paula Bennett would not comment on whether she would stand as deputy for English or Coleman.
"I've got nothing to say. I'm just going to keep a bit of clear air."