Cathy McGowan and her enthusiastic band of volunteers are deploying a disarming charm to take on the Coalition rightwinger

"We sort of come up with the slogans on the fly," says a young man working for the insurgent independent candidate Cathy McGowan, as orange-clad volunteers sort donations, agonise over campaign leaflets and ladle home-made spaghetti bolognese into bowls around him in the Wangaratta office.

But McGowan's "a better future for Indi" and "putting Indi first" are no worse than efforts by Labor ("a new way") or the Coalition ("real solutions") – suggesting that a party apparatus doesn't necessarily provide better wordsmiths.

It certainly doesn't buy enthusiasm. McGowan's diverse band of volunteers is committed and refreshingly cynicism-free. They are desperately keen to unseat the local member, the Coalition's Sophie Mirabella, but they are going about it with disarming charm, rather than fire and brimstone.

McGowan has pitched herself as the anti-Mirabella candidate. While the Coalition rightwinger has a reputation for being divisive and abrupt, McGowan seems to want to give the voters of Indi a big collective hug.

"I like people, which helps," McGowan tells Guardian Australia, as we trundle along in the train to Benalla for the unveiling of her transport policy.

The likable McGowan won't directly criticise Mirabella, nor even mention her by name – "the sitting member for Indi", McGowan calls her. She has looked to build a coalition of voters using niceness.

It is an approach that reaped rewards, with a leaked email from a Mirabella staffer admitting that the incumbent has been "outgunned" by McGowan's refreshing campaign, which has more than 400 volunteers and has raised $82,000 via crowdfunding.

"I've had huge support from the community," McGowan says. "The campaign has been clear and authentic and the community gets that. It's David v Goliath and it'll be a miracle if it happens. We need a perfect storm of preferences. But it'll be very close."

ReachTel polling in Indi, a vast electorate in Victoria's north-east that encompasses Wangaratta, Wodonga and part of the state's snowfields, showed that McGowan is set to capture 25% of the primary vote, with Mirabella on 47%, down from the 52.62% of the primary vote she won in 2010.

The Greens and Labor have preferenced McGowan first. Meanwhile, Mirabella has raised eyebrows by preferencing McGowan, along with Labor and the Greens, below the Rise Up Australia party, whose leader has claimed that the deadly 2009 Black Saturday bushfires, which touched the far south of Indi, were caused by a God angry at the sin of abortion.

McGowan strategists believe that a 5% shift of committed conservatives from Mirabella to the independent will put her within striking distance of victory, if preferences flow favourably.

The term "grassroots campaign" is a trite one, but McGowan's bid is certainly built on consensus and is policy-, rather than personality-, focused.

McGowan, one of 13 children, worked for the Liberal MP Ewen Cameron for three years before switching to a career as an agricultural consultant, focusing on issues faced by women in rural areas.

She only decided to run after a community consultation, called Voices 4 Indi, revealed public dissatisfaction over health, broadband, political representation and other issues.

Even then, she had to be persuaded to run by a young cohort of staffers who are credited with creating a social media drive that has proved a cornerstone of the campaign.

"These guys were Indi expats in Melbourne," says McGowan, signalling to her tyro allies. "They had a dinner party and said, 'What's going on in Indi, who's doing something?' They felt no one asked their opinions on anything and no one cared that broadband, mobile phones and trains don't work up here.

"They said I ought to stand. I said I would but only if they help me. I couldn't do it by myself."

She seems in her element among rural voters, all smiles, pearls and a sweater slung over her shoulders.

She plonks herself next to someone she knows on the train and chats amiably, stopping only to hand a "Cathy 4 Indi" badge to the ticket inspector. Her team, of varying ages, are all in orange T-shirts, looking much like an extended family on a day trip whose washing hadn't dried in time.

McGowan says she is badgered by voters to say if she's aligned to the left or right, but she refuses to be placed on the political spectrum.

The policies she has released so far appear to diverge from staunch conservatism – she supports Labor's National Broadband Network over the Coalition's, is comfortable with same-sex marriage, urges compassion for refugees and wants the creaking train service fixed.

But McGowan says she is "absolutely" in favour of free trade and calls small business "the heart and soul of Australia".

"All the stuff the Coalition does to support entrepreneurship and economic development is great, but when it comes to rural Australia they fall short, such as getting us good broadband," she says. "Those other issues [such as gay marriage] don't fall into left or right. They are conscience matters."

But won't such progressive views put off the traditional tillers of soil who make up a large part of the electorate?

"People think if you vote conservative you don't have a heart, but that's not true," she says. "Rural Australia does have a heart. This is a caring community. After the second world war, Wodonga was a centre for refugees and they were warmly welcomed."

For many voters, however, McGowan's biggest draw is the idea that she can beat Mirabella. The shadow science minister has held the seat since 2001, but with a gradually decreasing vote each election, confounding the theory of beneficial incumbency.

Her critics claim this is because she has used a safe conservative seat as a springboard for her own political ambitions, taking the electorate for granted and not always endearing herself to locals when she does interact with them.

"She is rude, she is abrasive and you never see her at community functions, apart from when an election is on," says Jenny O'Connor, the Greens candidate who has run against Mirabella in every election since 2003, over a drink at a pub in Beechworth, a charming historic town not far from the NSW border.

"She hasn't been a good local member and that's why Cathy is doing well. The comments by [outgoing independent MP] Tony Windsor gave Sophie a shock, frankly.

"I've known her for 10 years and we get on OK but I've noticed she is a different person this campaign. She's had a slap and she knows it. She's lost her nerve a bit."

In June, Windsor said he'd give Mirabella the "nasty prize" when asked on the ABC TV show Insiders whether there were any MPs he wouldn't miss after his retirement from politics.

"She wins the nasty prize," he said. "The people of Indi, just have a look at your representative and see how much better you could do." Windsor said he would offer his advice to the McGowan campaign.

O'Connor says other issues have rankled with the voters of Indi: Mirabella's former relationship with an older man and questions about his will, and the "very hurt" Indigenous leaders upset with her for boycotting Kevin Rudd's apology to the Stolen Generations.

"That issue has never quite gone away," says O'Connor. "People don't like the disregard for other people's wellbeing that she represents. She has shown an extreme, hardline approach to human rights."

Worryingly for Mirabella, some Liberal voters also have misgivings, although they are not quite as strong as O'Connor's.

The small town of Whitfield, which pokes up from the greenery of the King's valley, represents the most rural part of a rural electorate. Even here, in what should be Mirabella's heartland, there is a willingness to consider McGowan.

"I'd call myself an apolitical Liberal voter, but I'm not a fan of Sophie Mirabella," says Neil Dickson, a customer service manager, in the town's pub. "She hasn't come across well with some of the things she's done on Q&A.

"She's not really in touch. We don't see her around here. I'm impressed with the way Cathy is listening to people and engaging them."

John Darling, a local grape grower, calls the Greens "extremists" and says that Kevin Rudd is a "psychopath". But that doesn't mean his vote will go to the Coalition, as it has done previously.

"The major parties are so disrespectful, so it's nice to talk to someone who actually listens," he says. "I'll vote for Cathy and hopefully even if she doesn't win it'll deliver a message to those who take safe rural seats for granted."

If McGowan does upset the odds and win – she is placed at around $3.50 by Centrebet, down from more than $50 at the start of the campaign – it's unclear how well her values of inclusiveness and consensus will fare in the Canberra bear pit.

Indeed, several Liberal voters I spoke to said they would stick with Mirabella because as a probable member of the next government, she'll have a voice at the top table. McGowan also faces difficulties if she is elected into a hung parliament.

"Cathy has run a fantastic marketing campaign and people are charged up by it," says O'Connor. "There's nothing offensive about Cathy – she's kind and articulate. She's almost like minor royalty."

"But you can't sit on the fence forever. You have to show leadership if you're elected. She's said she wants a bipartisan approach to asylum seekers – what is she going to do, call Tony and Kevin into her office and sort it out? That's just naive."

O'Connor describes McGowan as a "progressive National" on the political spectrum, but admits that others will find it hard to know exactly what she stands for.

Mirabella herself has played on the fact that she is an experienced MP with the clout of a major party behind her. An rookie MP with no powerbase and rather woolly promises won't get things done for Indi, she argues.

Sophie Mirabella says she has been fighting for better rural services for the past six years. Photograph: Alan Porritt/AAP

"I'm honoured and humbled by the support I have had from locals during this and the previous four campaigns – and this particular campaign is going very well; I'm very happy with it," she says in a statement to Guardian Australia.

"Like anyone on the frontbench of either side of politics, I always strike what I hope is the right balance between the two roles of a local member and a shadow cabinet minister."

Mirabella denies that she has ignored the electorate and says she has been fighting for better rural services for the past six years, only to be stymied by an indifferent Labor government.

"It's a very late and convenient conversion from some of them [her opponents] in the lead-up to an election, but I'm glad they are now finally admitting what I've been saying all along has been right," she said.

"It's also an admission from them that only a strong, stable Coalition government can secure and deliver the commitments and funding that's needed to address the key issues of concern in Indi."

So can McGowan actually win? The odds may be against her this time around, but running Mirabella close will, the incumbent's opponents hope, highlight their concerns.

"Whether Sophie gets in or not, the pressure is on her now, which is fantastic for Indi," O'Connor says. "And if we can all knock off Sophie, then that's a great outcome."