He said the TVNZ poll had Mr McVicar higher than in National's own polling, "but we acknowledge there is vote splitting going on there".
"I suspect more has come from National, and that may assist Nash winning the seat instead of Walford winning the seat. We'll find that out on the 20th."
The poll is good news for Mr Nash, who has staked his political future on winning the seat by refusing to go on Labour's list.
Labour leader David Cunliffe visited Napier to help Mr Nash's campaign yesterday. Mr Nash's personal support at 39 per cent is well ahead of Labour's party support which is on 25 per cent.
National had 44 per cent support and the Greens on 12 per cent.
Mr McVicar's candidacy has also lifted support for the Conservative Party - which was on 9 per cent, more than double its nation-wide support.
The seat was won from Labour by Chris Tremain in 2005 and he had a 3700 majority in 2011. Mr Tremain is leaving politics this election.
Although it is too late to withdraw a candidate, Mr Key could have sent a similar message to National voters in Napier as in Act, urging them to vote for Mr McVicar to ensure the Conservatives' vote is not wasted if it falls just short of five per cent.
Mr Key said he still believed the Conservatives' best chance of getting in was to reach 5 per cent to enter Parliament. It was up to them to try to win an electorate seat and he did not intend to help.
Mr Key had considered a deal for Conservative leader Colin Craig in the East Coast Bays electorate similar to that with Act in Epsom. However, he opted against it, saying it would mean National had to withdraw Murray McCully altogether and that was a step too far.
The Conservative Party is currently polling at about 4 per cent in several polls.
• The poll of 500 eligible Napier voters was taken between September 9 - 11, and has a margin of error of +/- 4.4 per cent.
