With opinion polls showing that Prime Minister Malcolm Turnbull is running even with his rival Bill Shorten in the closely fought election campaign, attention has increasingly turned to the third force in Australian politics - the Greens.
Despite being shunned as radicals by the ruling Coalition and Labor, the Greens are expected to boost their vote share in the July 2 elections. In the past decade, the party has gone from four MPs to 11, with 10 in the Upper House and one in the Lower House. It also has 23 MPs in state and territory Parliaments.
The party effectively holds the balance of power in the Upper House, where no party has a majority. More importantly, it could potentially determine who will be prime minister if the nation is left with a hung Parliament, meaning no party has a majority in the Lower House.
Founded in Tasmania in the 1970s, the party became a national movement in 1992 and is regarded as the world's oldest green party.
It draws support largely from younger voters and inner city electorates with a well-educated professional population, many of whom are former Labor supporters. But opponents say its policies are extremist and impracticable.
Ahead of the elections, the party has been campaigning on strong action on climate change, including a price on carbon emissions, and free university education. It backs a limit on tax cuts for those earning more than A$300,000 (S$300,800) a year and increasing the refugee intake from 13,750 to 50,000 a year.
Much of its hopes rests on its current leader, Dr Richard Di Natale, a sports-obsessed farmer and former medical doctor who became its leader last year and has sought to give it a fresh, modern image.
In an unusual move two months ago, he appeared in a glossy photo shoot for GQ magazine, wearing a turtleneck top, sleek suit and leather slip-on shoes with no socks.
"When you look at all these issues - climate change, refugees, treating people seeking asylum with an ounce of dignity, marriage equality - our positions are smack bang in the centre of progressive, mainstream politics," he told GQ.
Analysts say the party has benefited in this year's campaign because the major parties have been so vocal in criticising it, including signing unofficial "pledges" not to form power-sharing deals with it.
"Anything that draws the Greens into the race and makes them relevant is good for them - it makes them players, and that's what they need to be," a pollster, Mr John Stirton, told Fairfax Media last week.
Notably, Dr Di Natale did not take part in the first debate between the Labor and Coalition leaders last Friday. The parties have flatly rejected including him in future debates, partly because he has no chance of winning enough seats in the Lower House to become prime minister.
The latest Newspoll survey on May 9 showed about 11 per cent of Australians intend to vote for the Greens, compared with 37 per cent for Labor and 41 per cent for the Coalition. On a two-party basis, based on allocating voters' preferences beyond their first pick, Labor leads the Coalition by 51 per cent to 49 per cent.
An expert on Australian politics, Dr Narelle Miragliotta from Monash University, said the Greens would be a "formidable force".
"While the Greens are not contenders for government in their own right, they are important players coming into this election," she wrote on The Conversation website on May 11.