The Conservative Party vote is much higher in Napier than in nationwide polls, reflecting Mr McVicar's strong personal following in the electorate.
Massey University political marketing specialist Professor Claire Robinson said the poll showed Mr McVicar was stealing votes from Mr Walford and Mr Nash.
"He's clearly been stealing votes, probably off both National and Labour. It's situations like these that don't make it easy for any political party, if the vote is split three ways.
"Garth McVicar will be taking votes off Stuart Nash and Wayne Walford and it seems to be working in Stuart Nash's favour. McVicar needs to be focused on the Conservative Party vote rather than his electorate vote.
"Given that poll result, votes for Garth McVicar are wasted votes. He needs to be telling people to vote Conservative for their party vote and give National their electorate vote."
The poll was taken between Tuesday and Thursday last week and has a margin of error of plus or minus 4.4 per cent.
Six per cent of respondents were undecided or did not say which electorate candidate they supported while 10 per cent were undecided or did not say how they would use their party vote.
Mr Nash said last night he was taking nothing for granted and he had told his campaign team they needed "to make the most of every single hour of every single day" until Saturday's election.
"It's going to be a full-on, long week of going very hard," he said.
"We're not resting on our laurels by any stretch of the imagination. We're going to be working incredibly hard right up to election day."
Mr Walford said he remained confident.
"We're just going to continue shaking hands and knocking on doors, and getting the message out there," he said.
"Until they count the final votes we won't know."
Mr McVicar, who was the last of the three main candidates to enter the race, said he was happy with the poll.
"I always knew we were up against a couple of well-known brands in Hawke's Bay, but we're on the upward plane and from what I'm picking up the others are slipping."
He said the party had a good strategy planned for the last week of the campaign so was expecting support to increase by election day.
Mr McVicar's party leader, Colin Craig, was upbeat about the Conservatives' prospects in Napier when he spoke at a party meeting in the city yesterday.
"Garth has got nearly a quarter of the vote in Napier under his belt.
"He started five weeks ago," Mr Craig said. "Every day Walford and Nash lose support to this man.
"They're desperately hoping their support doesn't leak away so quick that Garth gets over the line on Saturday."