The Liberal Party is battling to hold a third Senate seat in Western Australia in Saturday's historic byelection for the upper house as an advertising blitz from mining magnate Clive Palmer begins to bite.
Polls - albeit with small sample sizes - are suggesting his Palmer United Party has doubled its vote to 10 per cent - enough, with preferences, to get a Senate position.
At stake is the ability of the Abbott government to pass legislation through the Senate. The loss of an upper house seat would mean the Coalition would need an extra seven votes to pass legislation in the upper house.
WA Senate poll: Widespread apathy is tipped to be the reason for a possible low turnout.
If the Palmer United Party picks up a Senate position, it will have three senators and the support of Ricky Muir of the Motoring Enthusiast Party, likely to be enough for him to block legislation in conjunction with Greens and Labor.
The Senate re-vote in WA was forced by the inexplicable loss of 1375 ballots by the Australian Electoral Commission in the September federal election.
Palmer United Party has spent more than the other parties combined on advertising and Mr Palmer has been in Perth all week.
Although he is a Queenslander, Mr Palmer is portraying himself as the saviour of parochial Western Australians, basing his campaign on a pledge to redistribute more GST revenues to the state.
He has been roundly criticised in the local media, with Perth's only daily newspaper regularly savaging him in news reports and commentary.
''He's copped a lot from the Liberal Party and he's got unfavourable coverage. There has been a lot of criticism of his ability to deliver on his promises,'' said Martin Drum, a political analyst at the University of Notre Dame.
''But he's also tapping into a vein of discontent … he's really trying to attract disconnected voters.
''If the Liberal Party loses that third seat, Palmer is likely [to] pick it up. That's why the Liberals are going so hard.''
The Liberal Party won three of six Senate positions during the half Senate election in September after snaring 44 per cent of the upper house vote. It needs just under 43 per cent of the vote to get a third Senator across the line in Saturday's Senate re-vote.
And, after a steep fall in support in WA following the election of the Abbott government, Coalition insiders are detecting a swing back to them.
''Whether it will be enough is another question,'' said one Liberal Party source. ''It all hinges on Clive Palmer and whether WA voters are buying what he's selling.''
Labor is portraying the WA Senate race as a referendum on the federal government's first seven months in power, stoking fears of cuts to health and education.
Unions held a large rally this week against cuts to schools by the WA state government.
In a dismal result, Labor won just one WA Senate position in September. Its campaign has been hit by controversy surrounding candidate Joe Bullock a right-leaning unionist who was convicted of assault in 1996.
Labor must improve on its 26.6 per cent vote in September and win a second seat to bolster new leader Bill Shorten, insiders concede.
Amid widespread apathy about the re-vote, Labor believes a predicted low turnout will hurt it more than other parties.
The Greens are widely expected to retain one Senate position, with candidate Scott Ludlam seen as enhancing their support.