The centre-left Labor party has led the polls for months and is tipped to squeak over the finishing line, making Bill Shorten the sixth prime minister sworn into office in a decade.
Out on the campaign trail, candidates have been egged, abused and a slew have resigned for racist, sexist and otherwise jaw-dropping social media posts.
Prime Minister Scott Morrison -- who came to office less than a year ago via a party coup -- has campaigned virtually solo. Many members of his cabinet have either quit or were so politically toxic he kept them away from the cameras.
Final polls put Shorten, a former union boss, and his allies around one-to-two percentage points ahead of governing Liberal coalition, but on track to secure the first centre-left parliamentary majority in six years.
An upset is still possible. Like elsewhere in the West, Australians hit with rising living costs, growing inequality and wrenching social change appear fed up with left-right contests featuring career politicians.
The election has seen a surge in support for outsider candidates -- -- who range from green-minded conservatives to populists to far-right extremists.
They include Clive Palmer, a brash millionaire echoing Donald Trump and vowing to "Make Australia Great", who looks set to win a Senate seat after a high-spending campaign that saturated the airwaves for months on end.
The outsiders carry clout because of Australia's compulsory ranked voting system and could decide the balance of power.
Traditional parties have struggled to hang on.
Shorten's approval rating stands at a meagre 39 percent, behind Morrison's less-than-stellar 44 per cent, according to a Newspoll survey released Monday.
The conservative Morrison has managed to narrow the gap on Labor in the final weeks with a relentlessly negative campaign, but still faces an uphill struggle to avoid becoming one of the shortest-lived premiers in Australian political history.
In a final pitch to voters this week, the 51-year-old -- who is backed by mogul Rupert Murdoch's fiercely conservative media -- warned that Labor's economic policies would put up rents, raise taxes, kill thousands of jobs and lower house prices.
"I'm happy for this election to be about who you want as leader. Me or Bill Shorten -- the 'Bill' you can't afford, or the Prime Minister -- in me -- that backs the hard-working, honest aspirations of Australians."
Shorten has vowed to limit tax breaks for the rich and promised to raise public spending on everything from cancer treatment to sports changing rooms.
His hopes of becoming prime minister may hinge on results in Queensland and his home state of Victoria -- where Labor's lead has proved more resilient and where climate change has been a important issue.
Changing political climate
From cosmopolitan Melbourne to dusty drought-stricken Outback homesteads the government's climate scepticism has proven a risky electoral gamble.
It remains popular with the party's base and with hard-hit mining communities, but has fallen out of favour elsewhere.
That could spell trouble for the Liberal party's traditional electoral coalition -- suburban economic conservatives and rural social conservatives -- which appears to be fracturing.
Both former prime minister Tony Abbott and current treasurer Josh Frydenberg are battling for their own suburban seats against independent insurgent candidates who have run on environmentalist messages.
"The coalition's reluctance on climate change is being seen increasingly by younger voters as part of its lack of vision," Australian National University senior fellow Mark Kenny told AFP.
"Climate change has come to represent not just the issue itself, but the difference between the two parties."
In rural areas too, farmers battered by a summer of record floods, drought and wildfires appear to baulk at the government's reticence to ween the economy off its dependence on coal.
A nationwide survey by the Australia Institute found that more than half the respondents believe the country is "facing a climate emergency" and support more policy action.
Whoever wins the election is likely to face an economy that is stalling, and an increasingly difficult balancing act on the world stage.
Both major parties have voiced their support for an alliance with the United States that has been put under extreme strain by Donald Trump's trade wars, disregard for multilateral rules and willingness to flirt with war.
Both parties have also struggled to explain how they would deal with a resurgent China that is both economically vital and more willing to bully its neighbours.