With Prime Minister John Howard and Labor Party challenger Mark Latham locked in a tight race for the top job, victory could well hinge on an unusual, long-standing feature of Australia's electoral system: the preferential ballot.
Rather than voting for individual candidates for Parliament, voters rank those running in their district in order of preference. If no candidate wins a majority of first-place votes, the outcome is determined by the preferential rankings. Members of the Parliament then elect the prime minister.
The system, used in few other places in the world, allows Australians to cast their ballots for minor party candidates without necessarily throwing away their votes.
"I think it's the most powerful vote anywhere in the world," said Kevin Evans, an Australian who serves as electoral advisor to the United Nations Development Program in Indonesia. "It actually means you can vote your conscience, without it helping the party you most dislike."
If the United States had a similar system for presidential voting, minor party candidates such as consumer advocate Ralph Nader could be selected as a first choice with voters knowing that their second-place votes would then go to the next candidate of their choice, Democratic Party nominee John F. Kerry or Republican President Bush.
"Preferences are more democratic," said Rod Tiffen, a political science professor at the University of Sydney. "You could vote for Ralph Nader and have it not be a wasted vote."
Australia has long been a leader in election innovations. It began using the secret ballot well before other countries; when it was adopted in the United States it was known as the "Australian ballot."