Updated 1.43PM: It's just a week since Winston Peters threw his hat in the ring to run in the Northland by election, but his impact is certainly being felt.

NewstalkZB political editor Barry Soper says a snapshot poll in the electorate shows he stands a good chance of cutting the blue ribbon in the seat.

National's held Northland for decades, but the TV3 poll of 500 voters puts Mr Peters support at 35%, five more than National's Mark Osborne and way ahead of Labour.

Voters seem to feel they were left in the dark by National over what was known about the police investigation into Mike Sabin before the election.

Winston Peters says National can't afford to be complacent in the traditionally safe blue seat.

"National's taken this electorate for granted for far too long, a lot of National party people at the heart level understand that. They've been ignored, not listened to."

Peters says he's getting increasing support because the electorate wants a strong MP.

"There are a lot of people here, previous National voters, who are very clear that they have been let down, and let down dramatically."

Winston Peters says National's targeting him, and the by election will be ugly.

Mr Osborne acknowledges Mr Peters is a tough competitor but says he's working really hard on the ground to get out an win the trust of voters.

"I'd rate my campaigning experience as limited, I was only selected on Saturday. But we've got a tremendous team around us, that's been really beneficial for me."

Mr Osborne is choosing not to dwell on what impact negative publicity his predecessor, Mike Sabin, might be having on his campaign.

""That's the past," he says.

"I'm looking to the future and looking at what we can bring to Northland, carry on the great progress we have."

Osborne says Northland will lose representation if voters choose Mr Peters over himself.

"If people vote for Winston, Northland will have one less MP. He'll already be there in parliament and instead of a National MP for Northland, New Zealand First will gain another list MP down in Invercargill, so it's important that people understand that." 

A win by Mr Peters won't change the Government but it'll make it more difficult for it to enact policy.