Here's an Australian election teaser: What's hard and green on the outside, spongy on the inside with a brown nut in the middle? An avocado... or, to the party's critics, the Australian Greens, led by Tasmanian Senator Bob Brown.
With the conservative government and Labor opposition neck and neck ahead of Saturday's election, opinion polls suggest the Greens could emerge as the country's third political force, which has worried its opponents.
 Greens leader Bob Brown could emerge as a kingmaker |
Deputy Prime Minister John Anderson said Senator Brown was a communist and warned Australians to be "very afraid" of his party, using more fruity imagery to describe the Greens.
"They are watermelons," Mr Anderson insisted. "Green on the outside and very, very, very red on the inside."
Mr Anderson and other sections of the conservative right are rattled because Bob Brown's party could prosper as a result of Australia's unusual voting system.
A newspaper advert placed by a Christian group claimed that Greens' support for reducing the age of consent for homosexuals was good news for child abusers.
And the party's policy of decriminalising drugs for personal use has been the focus of an election broadcast by the Family First party.
 Australia's voting system could benefit Greens candidates |
"Heroin, ecstasy. The Greens want to legalise the whole lot. Don't risk the extreme Greens holding the balance of power."
Jenny Leong, a Greens candidate, told BBC News Online she was disappointed in her rivals.
"It is upsetting," she said as she campaigned in Sydney. "Sure, there's a need for people to have the freedom to believe what they believe, but it's unfair when you start getting ads saying the Greens are supporting paedophiles."
In addition to their policies on drugs and homosexuality, the Greens advocate conservation of Tasmania's forests, greater access to renewable energy, and free public education from pre-school to university. They want Australia's troops out of Iraq and an end to free trade discussions with the US.
Key votes
The Greens are not just attracting attention because of their policies, though.
Australia's electoral system in the lower house - the House of Representatives - could mean that the Greens have an important say in some marginal constituencies.
The system is called preferential voting, and means if the front-running candidate gets less than 50% of the vote on the first count, votes for other candidates are redistributed.
Minor parties often strike agreements with other parties - called preference deals - which mean votes for them can be given to a major party.
In July, Senator Brown said the party would decide preferences electorate by electorate. However, on Wednesday Mr Brown said he would contact the 26 Green candidates who had chosen not to direct preferences to any party and tell them to hand them to Labor.
Seats in the upper house of parliament are allocated differently - by proportional representation. Here too, the Greens could do well.
They are hoping to end up with as many as nine out of 76 seats in the Senate - a significant increase.
Tanya Plibersek, a Labor candidate in Sydney, believes the system gives small parties like the Greens too much influence in the Senate.
"I think there is a danger that the whole of the democratic process can be held to ransom by a few people," she told the BBC. "It's important to have diversity of views, but it does make me uncomfortable if minor parties have the balance of power," she added.
Serious alternative
As the campaign draws to a close, the Greens' message has continued to attract interest among many voters.
"I think that they're a great alternative to the two major parties," one young Australian said.
A fellow commuter, Sarah, a 25-year-old travel agent, agreed.
"They've got my vote in the past," she said. "Yeah, I'll go for the Greens."
Greens leader Bob Brown has brushed off criticism of his party.
He told ABC radio that in the days of environmental demonstrations in Tasmania in the 1980s, threats of physical violence were common.
"I was followed down the street at night by a man with an iron bar and we had threats of terrible things happening if we turned up at protests - and that's gone," he said.
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It's important to have diversity of views but it does make me uncomfortable if minor parties have the balance of power 
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