Prime Minister John Howard and his Labor challenger, Kevin Rudd, have set out final campaign pitches as the hours tick down to Australia's election.
Mr Rudd (L) needs a large vote swing to defeat Mr Howard
Mr Howard warned that a Labor victory would fundamentally change Australia, while Mr Rudd said the country was "crying out for new leadership".
Opinion polls continue to put Mr Rudd ahead of Mr Howard.
Analysts expect a sizeable swing towards Labor, which needs a net gain of 16 seats to form a government.
Voting is compulsory and more than 13.5 million people are expected to cast their ballots.
The first polling stations are expected to open on the east coast at 0800 local time (2100 GMT).
Mr Howard, 68, has been in office for 11 years. In recent weeks, he has emphasised his economic credentials and warned that a Labor victory would threaten prosperity.
More than 13.5m of Australia's roughly 21m people are registered to vote
Electors will choose candidates for all 150 seats in the lower House of Representatives and 40 of the 76 seats in the upper house, the Senate
PM John Howard has led the conservative Liberal-National party coalition to four election wins since 1996 and is seeking a final term
Kevin Rudd is taking the centre-left Labor Party to the polls for the first time as leader
Election issues are the economy, environment and war in Iraq
"If you believe that our country is fundamentally heading in the right direction you should not vote for a change of government," he told a news conference.
"Because if you change the government, you will change the fundamental direction of this country."
He said that the election was still winnable. "I believe that there is a bit of a tide coming back. I sense it in the streets," he told Australian radio.
But the man he has to beat, 50-year-old former diplomat Kevin Rudd, has been out in front throughout the election campaign.
Mr Rudd's policies include ratifying the Kyoto Protocol and bringing Australian troops home from Iraq. He has portrayed Mr Howard as out of touch with public sentiment.
"Where Mr Howard has lost touch with those working families is that he runs around the country telling people that the economy is strong," he said.
"At the same time, working families are saying that if the economy is going so well, why am I finding it so tough?"
On Friday, three separate polls put Mr Rudd in the lead, but with greatly differing margins.
An AC Nielsen poll put Labor 14 points ahead, while a Morgan survey put the figure at nine points. A Galaxy poll gave Mr Rudd's party only a four-point lead - the best figure for the ruling Liberal coalition in months.
Labor needs a swing of 4.8% of the vote to capture the seats it needs to form a government.
Analysts have suggested the race could come down to results in key marginal constituencies, including Mr Howard's own seat in Bennelong, Sydney.