Steven Joyce has confirmed he will contest the National Party leadership.
Joyce says he believes he has a "goodly" amount of support, but not yet enough to get the job of leader.
Joyce's entry to the contest this morning means five of the 56 MPs are now going for the job.
The caucus will meet this morning for the first time since outgoing leader Bill English announced he was resigning.
Joyce said he had a "good bunch of support, which is not yet enough to win".
"But it's a good start and I'm looking forward to the debate over the next week."
He did not believe any of the contenders yet had the 29 votes needed to win.
Joyce was one of only two MPs English has said he told of his decision prior to resigning. Despite the advance warning, he said he had only made the decision to contest the leadership on Monday.
"I've been approached by a lot of people over the last few days, both inside and outside the caucus, and considered it carefully and then made the call."
Joyce entered Parliament in 2008 and has never served in Opposition before, something his rival Judith Collins has described as one of her selling points.
Joyce said while that was true, he had dealt in "oppositional politics" every election as National's campaign manager since 2005.
He did not believe having had to front on controversies that erupted during those campaigns had tainted him.
"What it shows is that I'm able to front and discuss difficult issues and that actually I have a lot of experience in communicating the party's position and managing issues.
And I think that's really one of the strengths I bring to the table."
Joyce said his bid was not motivated by self-interest or ambition, but he understood what kind of a country New Zealand could be and how to achieve that.
He said the leadership was not about the last nine years, but who was best to lead the National Party into 2020 and lead the country in government.
He said all his rivals brought their various strengths but he had "a blend of experience, a proven ability to get things done and also a strong vision for the future of the country based on what we have succeeded in doing over the last nine years".
"I think we can take it much further than that over the next 10 years if we make the right decisions for the country."
Joyce was in the negotiating team which dealt with NZ First after the election. Joyce said that did not mean he could not work with whichever party was required in the future.
Joyce told Newstalk ZB's Mike Hosking he was not troubled by National's three-point dip in last night's 1 News-Colmar Brunton poll.
Instead he took it as a reminder to people that being the largest party was not a given and good polling was not a given.
"You actually have to go out and earn every day the respect of the public and the right of the public to contest for the election in 2020. It's a contest of ideas and a contest of how well organised you are. And that's the challenge for our party."
Joyce trusted that he would have support in the caucus. He told Hosking he did not have a deputy in mind.
"There are some people that are going to absolutely support you and some people that will probably support you, it all depends on how it goes out."
Joyce believed the race was more important than any individual.
"It's all about the future of New Zealand. It's not about me," he told Hosking.
"I worry about the current crowd. I don't think they have a plan and where they have got a plan it will take us backwards."
"It's time to step up, if I believe in what I do believe in."
Joyce, 54, called the generational change argument "entertaining" - and noted that there was only 15 years between the five candidates for leader.
Joyce said he got on well with rival candidates Simon Bridges, Judith Collins, Amy Adams and Mark Mitchell - and said that they would all bring different strengths to the role.
He said one of the challenges of leadership was to bring the National team and their strengths together.
"My plan would be to lead the party in to the 2020 election - if given the opportunity to lead the country."
Joyce admitted it was a difficult decision to make as he has a young family.
But his passion for the future of New Zealand could not be ignored.
"We don't have to be average or mediocre. We can be pretty damn good. And that gives us the capacity to help people."
National's caucus will meet today for the first time since Bill English announced his resignation as leader. At least five MPs are now vying for their support after Mitchell's late entry yesterday.
Mitchell, an MP since 2011, entered the contest yesterday to go up against Collins, Adams and Bridges for the role, which National's 56 MPs will vote on next Tuesday. Joyce also confirmed his bid today.
The importance of the decision for the caucus will be emphasised by last night's 1 News-Colmar Brunton poll, which showed Labour's support had climbed to 48 per cent while National's had dropped to 43 per cent, down three points.
About three-quarters of that poll was done before English announced he was resigning a week ago.
Taken after Ardern's successful visit to Northland for Waitangi Day, it also cemented Ardern in as the preferred Prime Minister, getting 41 per cent to English's 20 per cent.
Much of Labour's surge was at the cost of its coalition partner NZ First (down to 3 per cent) and support partner the Green Party (down to 5 per cent). However, the drop for National will concern MPs as they face the uncertainty of how voters will react to a new leader.
Mitchell has ground to make up – his rivals have spent the past week rustling up support. Mitchell said he expected the contest to be close but believed he had enough support to give him a chance and he was in it to win, not just to raise his own profile.
The others have resisted saying who they would have on their front bench, but Mitchell said he would want Steven Joyce to stay on in finance if he was leader.
Mitchell denied he had come to an arrangement with Joyce and although he had spoken to Joyce, he had not told him he planned to say he wanted him in finance.
Mitchell said he had a lot of respect for Joyce after taking part in National's strategy team during the last election.
"My admiration for him grew, especially seeing what he had to deal with when the fiscal hole came up."
He insisted Joyce's claims of an $11.7 billion hole in Labour's books was not fabricated: "that hole is still going to emerge".
Mitchell announced his decision at the Orewa Surf Life Saving Club in his electorate; one of the onlookers was club coach and The Bachelor star Zac Franich.
The 49-year-old said politically he was a pragmatist who believed in people having choice in their personal lives.
Mitchell's rivals welcomed him to the competition, saying it was good for National's MPs to have choices.
Mitchell has a background as a police dog handler and Armed Offenders Squad member before living in the Middle East for eight years as a security contractor. That role included hostage negotiations and accompanying scientists from the Hague gathering evidence for the war crimes trial of Saddam Hussein.
Mitchell did not believe there was a skeleton in his closet, saying he would not have got into politics if that was the case.
Mitchell relied on that background to make his pitch to be leader, saying it had taught him how to build a tight team.
"The other thing is I'm not scared of taking on an opponent and that's going to be critically important in taking this Government on."
Mitchell has cordial relations with NZ First leader Winston Peters, which he said was courtesy of the Parliamentary Rugby Team.
However, Mitchell took a swipe at NZ First, saying the current Government was developing into one in which "you've got seven per cent that is starting to control 34 per cent [sic]".
"Winston's on notice that if I am successful in the leadership, then he's in Government. I'm in Opposition. We're going to hold them to account."
Mitchell and wife Peggy, the widow of rally car driver Possum Bourne, have five children between them.
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