Milne now keeps the note with her on the campaign. ''I carry it with me because it says a lot,'' she says. The Greens leader offers the anecdote as we stand in the campaign headquarters of Adam Bandt, her deputy and the sitting MP for the seat of Melbourne, who is fighting for a second term after his unlikely victory in 2010. On the wall, the countdown to election day is recorded in big black numbers on orange paper: on this day we are at the midway point, 17 days to go. The room is buzzing, young volunteers hovering over computer screens. To complete a scene that could have been put together by central casting, 14 bicycles are stacked against each other for support by the front door. Milne nurses a cup of instant campaign coffee. These kids are great, she says, but her party has supporters across the generations. Among the youthful enthusiasts are two greyer heads, for boomers have also come to the aid of the party. All of which will be needed in an election that will not only be a fight for survival for Bandt, made all the harder by the Liberal decision to preference Labor above the Greens. It will also be the first big electoral test for the Greens under Milne's leadership. The Greens were Bob Brown, the lanky and charismatic doctor-turned-environmentalist who largely defined the party. Under his watch, the party secured unprecedented national influence in the minority Labor government.

But that was 2010. Three years on, Brown has departed the national stage, handing over to another warrior from the Tasmanian green movement trenches. Under Milne's leadership, the Greens walked away from the alliance with Labor. On September 7, will the Greens remain the third force in Australian politics? That force now consists of nine senators, who held the balance of power, and Bandt in the House of Representatives. At the last election, the party recorded a primary vote of 11.8 per cent in the lower house, and 13 per cent in the Senate. The polls now have the Greens at about 9 per cent, and Bandt in a difficult fight that will require him to improve his primary vote by several points. The nature of the campaign so far has been the fixation on the leaders of the two main parties, understandable to the extent that it will be Tony Abbott (probably) or Kevin Rudd (less likely) who will form government and occupy the prime ministership. So it is that their every step or misstep is recorded, dissected and interpreted. But what of the third force and its leader? Can the momentum of 2010 be maintained, and has Christine Milne emerged fully from the long shadow of Brown to stand politically in her own right? Milne is on a morning train to Ballarat, heading to the regional city for a day that will include talking to University of Ballarat students about university cuts. Mid-campaign, she is preparing for the official ''launch'' of the Greens campaign in Canberra on Saturday.

She is confident the Greens will hold all their seats. The critical areas are, of course, the seat of Melbourne, and Senate seats in Western Australia and South Australia, where Scott Ludlam and Sarah Hanson-Young respectively are fighting it out with conservatives. ''Those two electorates are crucial for people to make a choice between Tony Abbott or the Greens holding effective balance of power in the Senate,'' she says. This campaign is not 2010, when the Greens recorded the highest vote for a third party since World War II. Milne says the Greens had several things running in their favour, not least of which was a big community campaign on climate change. Abbott wasn't offering anything, and Labor had backflipped. ''There was a huge disappointment across the community that Labor had sold out on the climate,'' says Milne ''They knew that the Greens were consistent and would always stand up strongly on climate policy.'' Then there was the Greens' ability to mount a competitive advertising campaign, thanks to Wotif founder Graeme Wood giving the party $1.6 million.

These factors certainly helped the Greens achieve their best national result, but three years on, it is a tougher era for progressive parties. As Milne notes, the country is going conservative, as evidenced by the swing to conservative state governments. And in 2013, there is no such white - or green - knight with deep pockets to fund the same level of advertising. But as Milne points out, social media is now a bigger force in Australian politics, and this is the domain of younger voters who support the Greens. And there is the expectation that Abbott will win - something that will run in favour of a third party with a crucial role in the Senate. Milne believes there is a degree of nervousness in the community that will build in the last two weeks about giving Abbott unbridled power in both houses. ''People will not want him to have absolute power and will not want him to have control of the Senate,'' she says. Arguably, just as important for voters is the Greens' asylum seeker policy, which would close down the likes of Manus and Nauru and increase Australia's refugee intake. Milne likens the strong community reaction against the hardline policies of Labor and Liberal - ''one-upmanship in cruelty'' - to the big community campaign in 2010 on climate. ''I think the pendulum has reached its extreme and has started to swing back, as the community has said enough is enough: these are real people,'' says Milne.

There were legitimate questions over whether the Greens would founder after Brown's departure, but Milne has impressed with her own style in the role. While they share a common background in the Tasmanian green movement, she is not Bob Brown. Monash University's Paul Strangio says that now, more than a year after succeeding Brown, Milne has established her identity as the party's political leader. ''What she has not been able to do is fill the larger space that Bob Brown occupied as the Greens' political and spiritual leader,'' says Strangio, an associate professor in the politics school. ''Brown's had a unique public persona and traction that neither Milne nor any of her fellow Greens members was ever likely to match.'' Milne inherited the leadership at a time when there were already signs of a plateauing of support for the Greens following a decade of uninterrupted growth in the party's vote in the previous four federal elections, he says. And she also faced significant early challenges - volatility in the politics surrounding asylum seekers, and the pre-election distancing between the party and Labor. ''In the circumstances of a disappointing result for the party at the election, Milne's leadership might come under pressure from the younger generation of Greens politicians,'' says Strangio. ''On the other hand, the advent of an assertive first-term Coalition Government will potentially afford opportunities for Milne - or another leader of the Greens - to galvanise the party and its base.''

After Julia Gillard's demise, Milne is also the only female national political leader. She notes that the two big parties are now led by married men, each with three children, both of whom go to church on Sunday. ''People who have difficulty with women in leadership are quite satisfied now that the stars are aligned and everything's back as it should be,'' says Milne. ''That's a tragedy in Australia because women in leadership have a lot to offer.'' Her leadership of the Greens, she explains, is therefore also about making it easier for the next generation of women to lead. On a non-trading Wednesday, the Queen Victoria Market sheds are silent, except for the beeping of reversing forklifts and trucks preparing for retail battle the following day. Across the road from the appropriately named Soapbox store, Milne and Bandt have gathered for a suitably Green announcement: renewable energy. The community-owned project, costing $100 million, would allow communities to set up their own clean energy generators, such as solar parks and rooftops. The Community Power Agency has come armed with a solar panel, and groups from around Melbourne have gathered in support. As if to make a point, the sun is shining. The atmosphere, if not the temperature, is warm.

The media conference is delayed. Abbott is holding a press conference, and before the two cameras roll (ABC and Sky) the Greens want to see what he is announcing. The news comes through: $5 million for a stadium upgrade for the Brisbane Broncos NRL club. Milne wants to get started. ''Why the Broncos?'' asks Milne of no one in particular. ''Why not a community surf club or a girls' hockey club or something?'' Backed by community energy activists, she makes the announcement (the backdrop is the organic produce shed), and then there is time for photos with Milne and Bandt. The renewable people gather around for shots with the pair. In this setting, they are rock stars. I notice Milne is standing away from the group. Phone to her ear, her head tilts down as she listens intently. She wraps an arm around a flagpole. Is this a moment of political drama unfolding before our eyes? Not quite. The Big Brother television reality show has asked the leaders to record a message for the housemates, who are unaware an election has been called. In return, Milne is also largely unaware of what's happening in the Big Brother house. Federal election campaigns will do that. So the phone pressed to Milne's ear belongs to a community energy supporter whose housemate watches the show. The housemate is now briefing Milne.

Back at Bandt's campaign headquarters, Milne is largely drawing a blank as she continues her research and asks the young volunteers what they know about Big Brother. Fully engaged in supporting the cause, it isn't much. She gives a stirring address to the group. ''It's make or break for us,'' she tells them, urging them to keep up the doorknocking, the face-to-face campaigning. ''Make no mistake. At least 15 per cent of people haven't made up their mind how they are going to vote until they walk up the path on polling day. ''The only thing that will frame the vote for many of them is if somebody knocked on their door or said to them at the stall, or on the day, they see a Green person smiling at them and saying hello and asking for their vote, that will be enough.'' Troops rallied, Milne tries out a possible message for the Big Brother housemates. In the 2010 election, the Adelaide Zoo followed in the footsteps of Paul the Octopus, who correctly picked 2006 soccer World Cup winners. Photos of Bob Brown, Julia Gillard and Tony Abbott were placed with the giant pandas. They chose Brown. It was repeated this year, using orang-utans. Milne was chosen, although they chewed her left ear - perhaps upset that polling day is also Threatened Species Day. Abbott ended up in the dirt, while Rudd was eaten. (In the end, with only a three-minute Big Brother slot, she opted for a simpler pitch about the Greens.)

Signs from the animal kingdom are not unheard of in Greens politics. Milne says she is not really an omens person, but recalls the symbol of the Tasmanian Greens was the endangered white goshawk. If one was sighted before polling day, it usually meant a good result. Loading Orang-utans are, of course, also endangered. Milne is planning to visit the zoo and the orang-utans who chose her ahead of Rudd and Abbott before September 7. ''I think it bodes well,'' she says.