7.30pm - UPDATE
National MP Nick Smith's short tenure as deputy leader ended today after he learned he no longer had the confidence of his party leader.
A "disappointed" Dr Smith resigned when told National MP Gerry Brownlee would be challenging him at tomorrow's caucus meeting with National leader Don Brash's backing.
"The key issue for me was whether I had the confidence of the leader and after I received advice just after midday today that Gerry would be challenging, I phoned the leader. He advised me that he would be supporting that challenge and on the basis of that I tendered my resignation," Dr Smith said.
The overwhelming majority of caucus appears to have been ready to fall in behind whoever Dr Brash backed, despite the fact Mr Brownlee also has his detractors.
Dr Smith was deputy leader for less than three weeks, spending most of that time on leave for exhaustion.
When elected leader on October 28, Dr Brash supported the caucus decision to elect Dr Smith as his deputy and spoke about how it would unify the caucus camps in having a personal friend of ousted leader Bill English in such a senior post.
However, since then Dr Brash is understood to have become concerned -- perhaps after having his ear bent by more experienced politicians -- about putting too much pressure on Dr Smith who has been described by a party insider as becoming emotional under stress.
Dr Brash described Dr Smith today as one of Parliament's hardest working MPs, who was one of National's "star performers" in the debating chamber, and a passionate advocate for his Nelson constituents.
Dr Brash issued a statement today, saying that after consulting members of the caucus he had personally advised Dr Smith that standing down would be in his own personal best interests and in the wider interests of the party.
Mr Brownlee did not put his name forward when the vote was taken three weeks ago but sources said the party leader believed he and Mr Brownlee would complement each other -- Dr Brash's reserve offset by the outspoken Mr Brownlee.
Dr Smith took leave from work only three days into the deputy leader's job and after a row with chief whip John Carter who helped count the leadership vote.
He told NZPA he took two weeks' leave because he was exhausted "and I was emotional".
However, with large numbers of staff losing their jobs, recognising the toll on Mr English and his family who had put years into supporting his leadership, "you would be insane or inhuman not to have emotions".
"I am very disappointed that during this period a campaign to oust me was conducted in the media while I was under the leader's instructions to make no comment. Many of the reported statements concerned myself are incorrect."
Dr Smith handed in his resignation to Dr Brash at 3pm after hearing from Mr Brownlee that he intended to challenge.
He was disappointed Mr Brownlee had not put his name forward three weeks ago and had not told him of his challenge until this afternoon, but said he would not bear grudges.
Only last Friday, Dr Brash authorised a statement from Dr Smith in which he said he was looking forward to getting back to work.
Politics was a "rough business", Dr Smith said.
"Every job has its good and bad sides. There's lots of really positive parts of being a Member of Parliament. Sadly there are some parts of politics that are unsavoury but it seems it just goes with the job.
"I do hope, though, that the National caucus can change its culture because it's in New Zealand's interests that there is a Don Brash-led government after 2005 and we will not get there if there is the ongoing sniping that occurs between caucus members."
Dr Smith, saying he was a "loyal National Party soldier", said he had great respect for Dr Brash although he was disappointed he had made the decision he had.
It was with regret that he was resigning "but I have been forced into this position".
Meanwhile, Dr Brash must be hoping this will be the last change to National's line-up for a while -- with the exception of the return to the fold of suspended Maurice Williamson in the next month.