Tony Abbott’s “sex appeal” candidate, Fiona Scott, is poised for a landslide victory in the litmus-test western Sydney seat of Lindsay with a stunning 60% of the primary vote, according to a Guardian Lonergan poll.

Scott’s huge lead over the sitting member, the assistant treasurer, David Bradbury, who has held the marginal seat since 2007, surprised even the pollster.

“Given the size of the swing, we have triple-checked the data and we are very confident this poll is accurate. We asked respondents how they voted last federal election. When we model this historic data we would have predicted Bradbury to be elected over Scott with a two-candidate preferred vote of 52%, which is very close to the actual 2010 poll result of 51%,” Lonergan research managing director Chris Lonergan told Guardian Australia.

The poll, with a margin of error of 3.7%, was taken the night after an exuberant Abbott campaigning in the mortgage-belt seat likened his candidate to former Liberal member Jackie Kelly because they were both ”young”, “feisty” and "I can probably say they have a bit of sex appeal”.

It showed Scott with 60% of the primary vote, compared with 43% at the last election, and Bradbury on just 32%, compared with 45% in 2010.

The certain defeat of scores of New South Wales MPs such as Bradbury was a driving reason behind Labor’s decision to oust former prime minister Julia Gillard in June in favour of Kevin Rudd, who, according to polling at the time, was much more popular in marginal electorates.

But a 12% decline in Bradbury’s primary vote according to the Lonergan poll suggests the Rudd honeymoon is waning in the west, and raises big questions about the effectiveness of Labor’s campaign.

Thirty per cent of Lindsay voters said the leadership change from Gillard to Rudd had made them less likely to vote Labor, 23% said it made them more likely and 47% said it made no difference.

On every measure, the poll shows voters in Lindsay – centred around Penrith – prefer Abbott to deal with the issues they most care about.

Of the 1,038 questioned in the automated telephone poll, 44% nominated the economy as the most important issue in the election and 67% said they thought the Liberal party was best to manage that issue, compared with 30% who preferred Labor.

Twenty-eight per cent of voters said leadership was most important to them, a sentiment both Abbott and Rudd have been tapping with their insistence that they have a positive plan for the country. But 61% of Lindsay voters said they thought Abbott had the most positive election messages and 33% thought Rudd was most positive.

Twelve per cent pointed to asylum policy as the most important issue and, despite Labor’s policy backflip shortly before the election when it decided to send all asylum seekers arriving by boat to Papua New Guinea, 67% thought the Coalition was more likely to stop asylum seeker boats and only 27% nominated Labor as best able to do so.

Having asked how respondents voted in 2010, the poll found that three out of 10 voters who backed Bradbury then are now not planning to vote for him, whereas only 6% have changed their vote away from Scott.

“I have been working in market research for 20 years, and this is one of the biggest swings that I have seen. There are a lot of disenfranchised Labor voters in the Lindsay electorate. Just 65% of those who voted for Bradbury in 2010 intend to vote for him again in September. In comparison, 92% of those who voted for Scott intend to vote for her again,” Lonergan said.

Nationwide polls are showing the Coalition leading by 52% to 48% in two-party preferred terms, putting Labor in a losing, but not an impossible position.

Lonergan acknowledged that the “national polls show the Coalition in front by a much smaller margin than this”, but said the Lindsay result in his poll “may be a combination of a swing against Labor that is under way and which is accentuated in this electorate with its strong focus on the economy”.

Bradbury had his own controversy earlier in the campaign when he questioned whether a radio interviewer was biased towards the Liberal party and later admitted he had “got it wrong”.

Lindsay has been won by a representative of the winning party at every federal election since its creation in 1984.

Before 1996 it was a safe Labor seat, then it was held by Kelly during the Howard years before being won by Bradbury when Labor won office in 2007.