National's Napier candidate, Wayne Walford, says his party's internal polling has him trailing Labour rival Stuart Nash by 10 per cent.
But both candidates say their focus is on working hard as they approach "the one poll that counts" - the September 20 election.
Online market iPredict, where punters can buy contracts on future events including election outcomes, is also predicting Mr Nash will beat Mr Walford - although the site's percentage prediction of that happening has fallen over the past month from about 78 per cent to 65 per cent.
"It's improving for me all the time which is great," Mr Walford said.
"I'm just getting on and doing the work - shaking the hands and meeting the people and trying to unpack the scaremongering for amalgamation."
Mr Nash has aligned his campaign with a "no to amalgamation" message and Mr Walford last week welcomed news from the Local Government Commission that it did not intend to issue a proposal on the issue until after the election.
Mr Nash said Labour would not be conducting its own polling specific to the Napier electorate. He said poor poll results discouraged campaign workers and positive polls could make them complacent.
"Even if I did have an official poll that showed me at 60 per cent or 75 per cent I wouldn't believe it and the team and I would continue working as hard as we possibly can up until the evening of September 19," he said.
In the neighbouring Tukituki electorate, sitting National MP and Cabinet minister Craig Foss and Labour challenger Anna Lorck both said they had not been polling.
The iPredict site rates Mr Foss' chances of being re-elected at 97 per cent although the figure is an anomaly because no contracts have been traded.
Contracts for future events are bought and sold on the site then cashed in for $1 if they come true, or have no value if they don't happen.
"iPredict had me retiring at about 85 cents a few months ago and I'm now down to about 2 cents, so you take it all with a grain of salt," Mr Foss said.
Ms Lorck said the only polling she had been doing was door-knocking voters.
"When it comes to predictions and polls I'd be more inclined to ask the voters of Mahora and Frimley, who based on past election-day results have been very good at indicating who will be in government." Meanwhile, Mr Foss said he was expecting delivery any day of a large number of billboards featuring images of himself alongside Prime Minister John Key.
"We've put in one of the largest billboard orders of any electorate in the country and the Bay will be very much billboard blue very soon."