Mr Osborne has one massive advantage: an inherited majority of almost 10,000. But he's a political rookie and National is clearly wary of a blunder in a byelection, which attracts more intense attention than general election battles. When Mr Osborne rings for an interview, he has a babysitter with him from National HQ and talks on speaker phone.
The caution is understandable. Not only is he up against the unpredictable Mr Peters, but the background to the byelection was the resignation of Mike Sabin after reports of a police investigation dating back to last year.
Mr Osborne will be the one to find out what impact Mr Sabin's resignation has on that majority. He was Mr Sabin's electorate treasurer, although it's understood they were not close.
Mr Peters and Ms Prime both think Mr Sabin's resignation will have an impact. Mr Peters questioned if Mr Osborne knew about the problem earlier, given he was his electorate treasurer. Ms Prime said people would look at the factors that led to the byelection. "Everybody is interested in who knew what, when. The kumara vine in Northland works really well."
Mr Osborne says the first he knew of Mr Sabin's problems was when the matter became public in the media. "I had absolutely no knowledge of the personal issues that led him to resign. I'm focused on ... continuing National's track record here."
Mr Peters is pushing the line National takes the seat for granted. Mr Osborne counters: "We're taking nothing at all for granted. National has held the seat for many years, but what's important is gaining the trust and respect of the people. That's what I'm out there doing."
However, it will not help that he's not attending the first of the community "meet the candidates" functions on Sunday. He said he would be on a televised candidates' debate for TV3's The Nation tomorrow and attend other community debates.
There were split views within Labour over whether it should stand a candidate at all to increase Mr Peters' chances. If anyone has suggested Ms Prime take it easy on Mr Peters to boost his chances, nobody passed the message on. Asked what she thinks Mr Peters' motivations are for standing, she says: "I think he's there politicking."
Mr Peters' candidacy may boost the turnout of National voters wary of weakening the party's majority. Focus NZ candidate Joe Carr thinks so. "He's a very personable guy, a consummate politician. But they're quite conservative in Northland and they're concerned about Winston destabilising a National Government."
Act's candidate, Robin Grieve, has pointed out NZ First did not bother to stand a candidate in Northland in the last election and Mr Peters lives in Auckland. "The last thing we need is a career politician parachuting in and trying to run a dirty campaign to increase his own profile."
Mr Peters is sensitive to suggestions he is using Northland. His press secretary texted his focus areas as including "the forgotten North" after an interview.
It's Winston first - and heat is on
Labour could come under renewed pressure to do an Epsom-style deal with NZ First leader Winston Peters after the first public poll of the Northland byelection showed he has an early lead.
The 3News Reid Research poll of 500 Northland voters showed Mr Peters on 35 per cent and National candidate Mark Osborne on 30 per cent.
Labour's Willow-Jean Prime was on 16 per cent and 19 per cent of those polled chose other candidates or did not know.
It would be a big upset if the poll result were also the result of the March 28 byelection. National has held the seat for decades and former MP Mike Sabin had a majority of more than 9000 votes last year.
The results indicate the contest is closer than is comfortable for National
But Mr Peters cannot rest on his laurels. National has a strong grassroots machinery in Northland and the prospect of losing the seat could galvanise the party's turnout.
The poll result will raise further questions about whether Labour should give the nod to its voters to support Mr Peters to help him win the seat from National.
It is too late to withdraw Ms Prime, but Labour could cut a deal similar to National in Epsom and Ohariu by telling its supporters to vote for Mr Peters instead.
It is understood some in Labour believe Mr Peters should get a clear run.
Labour and Mr Peters have criticised National's deals with United Future's Peter Dunne and Act's David Seymour in Ohariu and Epsom, but Labour leader Andrew Little said that was not why Labour opted against pulling out of Northland.
He downplayed Mr Peters' chances, saying he was not convinced the NZ First leader could win.