"We are in a byelection, we are fighting hard, we know we're up against it. You've got all the other parties coalescing round Winston but we've got a great candidate and a lot of National voters here. The real challenge is will those voters actually turn out and vote on Saturday. If they do, we can win the byelection, if they don't, we won't."
Asked how National could be in such danger in a supposedly safe seat, he said byelections were very different from general elections - turnout was usually much lower and the focus was on local rather than national issues.
"And you have got someone with amazing name recognition in Winston Peters up against a new candidate."
Mr Peters said he was "not overconfident" but believed he could pull it off because National voters were angry with the Government.
"Right now we're pulling more National voters than Labour voters. That's because the National Party voters up here are brassed off about the [Mike] Sabin issue, the way it was covered up and the way they were left out. And they're brassed off, the farmers and other people, with the way they've been treated."
Mr Key said there were reasons why he could not comment on the issues around former MP Mike Sabin and he would talk about it if those reasons changed. He did not believe it had damaged the credibility of the Government in Northland.
The One News Colmar Brunton poll of 501 eligible Northland voters was taken from March 22 to 25 and has a margin of error of plus or minus 4.4 per cent.