Exclusive: Poll puts Jason Ball in lead on two-party-preferred calculation, even though Greens’ primary vote is one point behind Labor

New polling in the Victorian seat of Higgins suggests the Greens candidate, Jason Ball, could take the seat from the Liberals in a major upset on 18 May.

An interview poll of 400 respondents in Higgins undertaken for the Greens by Environmental Research & Counsel puts Ball in the lead on the two-party-preferred calculation, even though the Greens’ primary vote is one point behind Labor.

The Liberal vote in the survey is languishing on 36%, Labor is on 30% and the Greens are on 29%. Liberal strategists say if the primary vote in Higgins falls below 45% either Labor or the Greens will take the seat, which has been held by retiring cabinet minister Kelly O’Dwyer since 2009.

The Greens argue they can win Higgins from third position because there is no strong independent in the field – unlike the adjacent Kooyong contest – and because of beneficial preference flows from micro-parties such as the Animal Justice party.

If that scenario came to pass, it would replicate the result the state MP Sam Hibbins achieved in Prahran in the two last state elections. The new poll’s two-party-preferred calculation is 54% Greens, 46% Liberal.

While single-seat polls can be unreliable, the new survey, if accurate, suggests the Liberals are in terrible trouble in the Victorian seat they hold on a margin of more than 7%, with both the Greens and Labor in the hunt. The Liberal candidate in the seat is paediatrician Katie Allen.

Labor, which is running high-profile barrister and former Law Council of Australia president Fiona McLeod in the contest, has pumped negative material into Higgins in the closing week of the contest reminding voters of the conservative-led move against Malcolm Turnbull, with a tag line: “Is this the Liberal party you voted for?”

Play Video 6:28 Higgins: why is the Liberal heartland turning its back on the party? – video

Ball says the “crash” in the Liberal party vote in Higgins and neighbouring electorates “shows a community that has had enough”.

“There’s only so many times you can take this community for granted, and now they’re fighting back at the ballot box,” the Greens candidate said.

The Greens leader, Richard Di Natale, said voters in Higgins could deliver a seat once held by Harold Holt and Peter Costello to the Greens. “You can bring an end to the climate wars and transition our economy to a renewable energy future,” Di Natale said.

The poll suggests 70% of respondents rated climate change as either extremely important or very important to them in this election contest, and 83% expressed negative views about in-fighting within the Liberal party.

If the Liberals lose Higgins on Saturday night, there will be a robust internal reckoning about how resources were allocated during this contest, with Josh Frydenberg’s Kooyong campaign a major focal point for the party.

The major party leaders have increased their daily tempo as the election campaign moves into the final week. Scott Morrison campaigned on Monday in Sydney and in Perth and is expected in South Australia on Tuesday.

Bill Shorten campaigned on the central coast of New South Wales before relocating to Tasmania on Monday night.

While there has been a rush on early voting, MPs on both sides are nervous about how undecided voters will break in the final week of the campaign. The latest opinion polls indicate Labor remains in front in the contest as it enters the home stretch, but MPs are conscious a sizeable chunk of voters remain on the fence.

The contest looks tight and no one is sure how sentiment is firming in the two Northern Territory seats and in Tasmania. There is a near universal view that Australian voters will deliver different results in different parts of the country on Saturday night, rather than a uniform swing, and if that comes to pass, it suggests the result will be close.

• On 14 May 2019 this article was amended. A previous version wrongly stated the poll’s two-party-preferred calculation.