The Liberal, Labor and the Palmer United parties were set for a hard-fought three-way contest for the final two West Australian senate seats late on Saturday night.
An hour after the polls closed on Saturday night, Liberal senators David Johnston and Michaelia Cash were tipped to win their seats, as were Labor's controversial candidate Joe Bullock and the Greens' Scott Ludlam.
With early indications of a 15 per cent drop in voter turnout, Labor's Louise Pratt, the Liberals' Linda Reynolds and Palmer United Party's Dio Wang were considered the front-runners to claim the final two seats.
Voters may have to wait weeks before the final two seats are decided.
The byelection comes after a week of high drama, with the Coalition stepping up its political attack on the Palmer United Party – which has outspent all other parties on advertising – and amid fears the government could suffer a protest vote that would benefit Mr Palmer's party.
It also comes after a recording emerged of Mr Bullock praising Prime Minister Tony Abbott, criticising his colleague Senator Pratt and admitting he did not always vote for the ALP.
Senator Pratt played down the impact of Mr Bullock's remarks on the Labor vote on Saturday night, as did Mr Bullock.
“We've been campaigning hard here for a month," he said. "Campaigning on the issues of health and education and attacks on workers' standards of living. We're confident that that momentum from that campaign will be the thing that lingers in people's minds."
He ruled out any prospect that he could quit the ALP and sit on the crossbenches, declaring his “heart and soul” were with the Labor Party.
Labor has been campaigning on state-based issues, highlighting cuts to health and education by Colin Barnett's government, while the Coalition has emphasised its promise to repeal the carbon and mining taxes.
If the Coalition wins two seats in the West this time around, it will need seven votes from the crossbench to pass legislation through the Senate.
Senator Ludlam said he was hopeful of claiming a full quota on Saturday night and played down the Greens' recent poor showing in Tasmania.
"So this time, we were talking about the Senate and we were just talking about Western Australia," he said.
"I've got to say it's been I think quite a good exercise for West Australians to find their political voice.”
For key legislation such as the repeal of the carbon and mining taxes, those votes will most likely come from the two or three Palmer United senators, the allied Motoring Enthusiasts Party, the Liberal Democratic and Family First Parties as well as Democratic Labor and Senator Nick Xenophon.