Labour Party leader Phil Goff says National must be worried about its candidate losing New Plymouth if it has decided to have John Key visit the seat twice during the election campaign.
National's Jonathan Young holds New Plymouth by just 105 votes, making it the most marginal seat in the country.
Mr Key was in the New Plymouth electorate on 7 November and will return later this week.
Mr Goff has not visited the seat during the official campaign, but says he was there with the Labour candidate Andrew Little twice earlier this year.
He says Mr Little, a former president of the Labour Party, has run a strong campaign and has a really good chance of winning the seat.
"He's an accomplished candidate - much stronger than you expect for a first-time candidate - because he's got experience. He's a hometown boy and he's fighting against a person that probably a lot of people couldn't identify as their local MP."
National leader John Key also says Mr Young is running a good campaign and will do well at the polls on Saturday.