Steven Joyce and Judith Collins may be involved in an unofficial leadership contest within National to take over when John Key finally leaves politics, but neither is seen as the best replacement were it to happen tomorrow, according to a New Zealand Herald DigiPoll survey.

Finance Minister Bill English is the preferred choice of general voters.

Mr English was favoured by 29.7 per cent, Mr Joyce by 25.4 per cent and Ms Collins by 13 per cent. Almost 20 per cent thought none of them.

Mr English has been Finance Minister since 2008 during the worst of the global financial crisis, and is Mr Key's Deputy Prime Minister. Mr Key declined to nominate a successor.


Asked at his post-Cabinet press conference who he thinks would be best to replace him if he fell under a bus, he said initially "someone with a sense of humour".

"We've got a very talented caucus and If I name one of them the other 58 ... will be bitter and twisted."

Helen Clark once nominated Trevor Mallard as her natural successor, early on in her prime ministership.

Mr Key has previously indicated he would leave politics if he were voted out of office. The unofficial leadership battle between Ms Collins, the Justice Minister, and Mr Joyce, the Economic Development Minister, is realistically for Leader of the Opposition and would be determined by National MPs, not voters.

A similar poll question was published last week in relation to Labour leader David Shearer: in that case the preferred replacement if Mr Shearer were to suddenly leave politics was David Cunliffe at 31.8 per cent, Grant Robertson with 16.7 per cent and Andrew Little with 13.5 per cent. A total of 27 per cent of respondents didn't know or refused to answer and 11 per cent said none of the above.