Steve Stefanopoulos and his now husband, Craig, were on holiday in Vietnam when Malcolm Turnbull defeated Tony Abbott in the Liberal leadership spill in September 2015. The couple clinked champagne glasses over dinner in Ho Chi Minh city, toasting Turnbull’s ascension to prime minister.

“We saw him as a conservative progressive Australian leader,” says Stefanopoulos, 43, impossible to miss in a bright red jumper as he strolls by the upmarket cafes and galleries of High Street, Armadale, in Melbourne’s east. “Unfortunately, he got ousted … people are still upset about Malcolm not being in government and the way the whole thing happened.”

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Stefanopoulos, 43, is the mayor of the city of Stonnington, a municipality in the middle of the electorate of Higgins. This is Liberal heartland. The party has held Higgins at every election since the seat was created in 1949. It’s the “leadership” seat – two prime ministers, Harold Holt and John Gorton, represented Higgins, as did the former treasurer Peter Costello. The prominent cabinet minister Kelly O’Dwyer is retiring at this election, and after a redistribution, the Liberals have a 7.4% margin.

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Yet this is small “l” liberal Melbourne, turned off in recent days by Liberal candidates hastily disendorsed for homophobic and Islamophobic remarks. Almost 80% of this electorate voted yes in the same-sex marriage plebiscite, the seventh-highest result in the country.

Higgins is changing. It may include the city’s wealthiest suburb, Toorak, with its stately mansions and Mercedes in the garage, but apartments are popping up in South Yarra, and on its western fringe, Prahran is edgier and grungier, and increasingly Green.

Stefanopoulos is a swinging voter and is yet to decide who he will support. The environment is his first priority. “I want someone in government who really believes in climate change and is going to act on that.”

For someone who has lived here all his life, Stefanopoulos has a message: “It’s to the detriment of the Liberal party if they forget who their base level constituents are. They need to come back here to their heartland.”

Facebook Twitter Pinterest Stonnington city council mayor Steve Stefanopoulos says Higgins is small ‘l’ Liberal Melbourne. Photograph: Christopher Hopkins/The Guardian

Higgins is normally an afterthought at federal polls, but not this time. The biggest surprise at the November state election was not that Daniel Andrews’ Labor government won, but the collapse of the traditional Liberal vote in Melbourne’s inner east. The seat of Hawthorn, near Higgins, fell to Labor without the party even trying. Malvern, within Higgins, swung 10% to Labor. Tim Colebatch in Inside Story transposed the state results over federal boundaries and found that if people voted the same way, Labor would win Higgins, something it has never come close to before. It’s a big “if” – people distinguish between state and federal politics – but for the first time, the Liberals are contemplating the unthinkable.

‘They’ve forgotten about us’

The state election was interpreted as the revolt of the faithful, that moderate Liberals were angry and embarrassed with the rightwing segment of the party that had for a decade resisted serious action on climate change, and stoked fears over social issues such as Safe Schools and “Sudanese gangs” in Melbourne.

O’Dwyer reportedly told colleagues in the aftermath of the Victorian result that the Liberals were regarded as “homophobic, anti-women, climate-change deniers”, hijacked on social issues by “ideological warriors”. That might work in parts of Queensland, but not in progressive Melbourne.

Facebook Twitter Pinterest Chapel Street, South Yarra. Much of the Greens’ state seat of Prahran is within Higgins. Photograph: Christopher Hopkins/The Guardian

John Ribbands is a barrister and president of the Prahran Junior Football Club. As the weak autumn sun sends shadows over the ground, he leans on the stadium banister and points to the apartments on the skyline. Middle-class families are moving in, and there are housing commission estates nearby too. The footy club is growing, especially with girls keen to play football, including Ribbands’ daughter. “We’re bursting at the seams. We have to turn kids away.”

Ribbands, 57, is weary of the turmoil of Australian politics. On both sides, “they’re so focused on themselves, they’ve forgotten about us”. He’s a Higgins-style Liberal.

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“If I had to nail my colours, I’d call myself a conservative with a social conscience. From an economic perspective, I’ve got concerns about Labor’s fiscal management. We’ve seen it over the decades, every time we have a change, you see the country goes into the red, and then Liberals come back in and bail them out of it.” And “to be perfectly blunt, I just don’t see Bill Shorten as the man to lead us on the world stage”.

He’s frustrated with the Liberals too. “[They] missed a wonderful opportunity to see themselves in government for the next 10 years by not electing Julie Bishop as their leader,” he says of the retiring former deputy leader. “The machinations which brought about the overthrowing of Malcolm Turnbull were led by Peter Dutton. It was internal infighting and no real consideration … about the future.”

Ribbands’ instinct is that the Liberals will come home on 18 May. The state result was about voters giving the party a “kick up the backside … frustration at the Liberals and where they’re at and what they’ve been doing” more than an endorsement of Labor.

Katie Allen hopes he’s right. The Liberal candidate ran at the state election in the seat of Prahran, which swung to the Greens. She’s a doctor of paediatrics at the Royal Children’s hospital, a researcher into childhood allergies, and has raised four children in the area. Allen, 53, is also independent-minded and outspoken, blaming the “federal fiasco” for the Victorian election. She is more diplomatic now.

Facebook Twitter Pinterest Liberal candidate Kate Allen speaks to voters at the pre-polling station at Malvern. When people ask what sort of Liberal she is, she says a Higgins Liberal. Photograph: Christopher Hopkins/The Guardian

“There were concerns about the issues that were playing out at the federal level and we did hear that,” she says, taking a break from handing out how-to-vote cards at pre-polling in Malvern. Since Christmas, people have been impressed with the Coalition’s “very strong economic agenda … a strong economy enables us to then invest in all the things that we need – health, education, infrastructure – but also a sustainable future.” On the day we meet, the party had disendorsed Jeremy Hearn as its candidate for the Melbourne seat of Isaacs over a conspiracy-laden anti-Muslim rant he posted online last year. That he was even preselected was a sign of the ideological turmoil within the state branch.

The comments were “completely out of step and out of place and completely unacceptable” in Higgins or anywhere else, says Allen.

“I have progressive views having lived in Higgins for 40 years. When people say what sort of Liberal are you, I say I’m a Higgins Liberal. I am a product of my environment.”

Target seat for Labor

Higgins is a three-horse race. In March, Labor, aware that the seat was a possibility for the first time, replaced its candidate with the prominent barrister Fiona McLeod SC, a former president of the Law Council of Australia who has headed up legal teams in the Victorian bushfires royal commission and the royal commission into institutional responses to child sexual abuse. The 54-year-old is also a campaigner for a federal anti-corruption commission.

But she has only had two months to campaign, doesn’t live in the electorate, and only joined the party a week before she was preselected. Labor’s vote was hopeless at the 2016 election, with just 14.95% of first preferences. It was tipped to second place by the Greens’ Jason Ball, who is standing again this time. But Labor barely tried last time and Higgins is now a target seat. McLeod, who wears a red jacket wherever she goes, exudes progressive passion.

Facebook Twitter Pinterest Labour candidate Fiona McLeod says many traditional Liberal voters realise the government no longer represents their values. Photograph: Christopher Hopkins/The Guardian

“Many people I know who were once Liberal supporters are so angry with what’s happening at the federal government level on so many issues,” she says over the buzz of her campaign launch at a hip restaurant in Prahran. “Climate change, what’s happened to Malcolm Turnbull, the fact that we have a PM who walks into parliament brandishing a lump of coal, the fact that we’ve had people stuck on Manus and Nauru for six years now with no action, and these are my issues, too.

“The fact that the Uluru statement from the heart is dismissed out of hand without consideration. They realise the government no longer represents their values.”

‘The best chance we’re ever going to have’

McLeod has so much ground to make up, there’s a chance that Allen’s real competition may be Ball, the well-known LGBTI campaigner. The idea that the Greens could win a seat like Higgins seems preposterous, but he got 25% of the first-preference vote last time, and believes Labor’s increased interest could help him. Much of the state seat of Prahran, which is a Greens seat, is within Higgins, and there are pockets to the east of the electorate that are less rusted on Liberal.

Facebook Twitter Pinterest Greens leader Richard Di Natale campaigns with Jason Ball, who says Higgins is a blue-green contest in a young and highly educated electorate. Photograph: David Crosling/AAP

Ball, 31, with his neat suit and boy-next door looks, was preselected more than a year ago, and has campaigned full time since November. He has 250 volunteers door-knocking and making phone calls, and has raised $250,000 in donations. This is a blue-green contest, he says, in a young and highly educated electorate.

“I feel like this is the best chance we’re ever going to have,” Ball says. “I don’t think Liberals will ever be this much on the nose. I don’t think climate change will ever be this much top of mind for the voters.

“I have never seen before this many people raise the environment and climate change with me, far more than the last election.”

One of them is Campbell Timms, 20, who stops to talk to Ball before voting. It’s Timms’ first federal election, and he’ll support the Greens. “I was mostly concerned about clean energy and the climate overall …. there’s lots more better alternatives to especially coal and better forms of energy development across Australia.” Over the next 20 years, he predicts, there’ll be more people like him. “It will be less of a safe Liberal seat.”

Facebook Twitter Pinterest Campbell Timms, 20, at the pre-polling station in Malvern. He thinks Higgins will be less of a safe Liberal seat in future. Photograph: Christopher Hopkins/The Guardian

The Greens have the most aggressive policies on climate change, including shutting down all coal-fired power stations by 2030. Labor’s target to reduce greenhouse gas emissions by 45% is more ambitious than the Coalition’s 26% target, criticised by environment groups and climate scientists as too weak.

Allen says there are other issues in Higgins – population growth, infrastructure, health and education – but she’s aware of climate change, too. According to a Roy Morgan poll, almost 67% of voters in Higgins named climate as their top issue, the highest response for any Liberal seat.

“What I say to them [voters] is that it’s not just an environmental imperative, it’s an economic imperative, that we move to a future that is going to move us off fossil fuels. But they want to hear a sensible, practical response because after 10 years of arguments about this, they want to hear what the plan is … people in Higgins can see when there are false promises being made.”

If this is a generational election, at least some retirees in Higgins are not happy. Jack Hammond is a retired barrister, and a few years ago founded Save Our Super to protest the Coalition’s changes to superannuation, including imposing a $1.6m cap on the amount of money that can be moved into a tax-free super account. It was Kelly O’Dwyer’s policy and Hammond, 76, was furious, not because policies should never change, but because the Coalition had promised no changes to superannuation. For him, it was a matter of trust.

Facebook Twitter Pinterest Malvern resident Jack Hammond will be disadvantaged by Labor’s changes to franking credit rebates. Photograph: Christopher Hopkins/The Guardian

He will be personally disadvantaged by Labor’s plan to end cash rebates for franking credits claimed by people who haven’t paid tax in that year. Labor says it’s a loophole that needs to be closed if it is to afford to spend more on services like cancer treatment and childcare.

“I’m not saying that governments should be precluded from ever changing laws,” says Hammond, “but when changes to superannuation policy and retirement policy in particular are made, there ought to be at the same time appropriate grandfathering provisions. It then remedies itself. Us old grey-haired people die and the younger people come through trusting the system.”

Facebook Twitter Pinterest One of Melbourne’s most expensive streets is St Georges Street, Toorak. Labor’s policies will redistribute money from wealthier people in seats like Higgins. Photograph: Christopher Hopkins/The Guardian

Labor’s policies will redistribute money from wealthier people in seats like Higgins. Gab Williams, an author, says the area is well-off and she’s happy for that shift to happen. “I feel like I live a comfortable life so I’m more concerned about making sure that people who don’t have so much are looked after.” Her father in law, though, is “really upset” about Labor’s franking credit reforms.

Local mayor Steve Stefanopoulos has never seen such attention on Higgins. Local radio stations set up outside broadcasts to gauge the mood. Ministers and shadow ministers are visiting. Millions are being pledged for sporting facilities and level crossing removals.

He believes all the major candidates are impressive, and he welcomes the contest. “Higgins has never been in play, never as far as I remember,” he says. “For some reason, we’re getting a change.”