NZ's next PM: The contenders

Prime Minister John Key's surprise announcement that he is standing down, after 10 years at the helm of the National Party and nearly nine as PM, will have the contenders jockeying for position before the caucus vote on 12 December.

Mr Key said whoever was chosen as the next leader would have his "unwavering support", but if his right-hand man - Deputy Prime Minister Bill English - put his name forward, he would support his bid.

Mr Key and Mr English have been the closest of partners but there will likely be challengers from the caucus.

Here's a quick rundown of who might consider themselves leadership material:

Bill English

A former leader of the National Party in the early noughties, Mr English has been a steady hand on the economic tiller and Deputy Prime Minister since 2008. He knows politics inside out - having been an MP since 1990 - and has held a number of other high-profile positions including Minister for Infrastructure and Leader of the Opposition.

Speaking at a media stand-up this afternoon, Mr English refused to be drawn on whether he would seek the leadership, saying he needed to talk to his family and members of the caucus first.

But Mr English said he would probably announce his decision tomorrow and wanted to make sure he had enough caucus support.

Mr English, who led the National Party to its worst election defeat in 2002, said he had learned a lot since then.

Former National Party president Michelle Boag and the ACT Party support Mr English.

Auckland mayor and former Labour leader Phil Goff said he was relaxed about dealing with a likely Bill English leadership.

Paula Bennett

The pundits have been singing Mrs Bennett's name from the song sheet for some time but the past year, with homelessness becoming a major issue, has probably soured the tune.

She is self-made after a tough start in life which included being a working solo mum. She has tackled some gritty portfolios, including Social Development, Employment and Local Government. She is currently the Minister for Climate Change, Social Housing and State Services.

Steven Joyce

Mr Joyce discovered world-wide fame after being hit by a dildo thrown at him at Waitangi this year, something which he responded to with nicely-judged humour.

He has been given the nicknames the 'Minister of Everything' and 'Mr Fixit' after investigating the Novopay mess and Fonterra's 2013 milk formula recall.

The Northland by-election didn't quite go to plan for the former broadcasting entrepreneur but he's another who has been close to Mr Key and has quite a bit of support in the business community.

Judith Collins

Also the holder of a few nicknames, including 'Crusher', Ms Collins was another favourite of the pundits and a number of the backbench - before resigning in 2014 over a ruckus involving the Serious Fraud Office. She returned from the wilderness late last year as the Police and Corrections Minister and still has a number of supporters in the party.

Among her ministerial responsibilities have been Justice, ACC and Veteran Affairs.

Mrs Collins has not ruled out a bid for the leadership. She said she would attend a caucus meeting tomorrow and see what happened.

Amy Adams

Probably an outsider at the moment, but worth a gamble in the office stakes, is Amy Adams.

The Justice Minister was recently named 2016's top politician by the beltway stalwart publication transTasman. Ms Adams has a reputation for getting things done and without too much fuss.

This year that has included the David Bain and Teina Pora compensation claims and chugging through a lot of new legislation.

She came into Parliament with Mr Key in 2008 and her responsibilities have included Minister of Environment and Communications.