The race for WA's last Senate seat could prove crucial to the passage or defeat of key parts of Tony Abbott's agenda if he wins the election tomorrow.
The Nationals candidate, former West Coast Eagles star David Wirrpanda, has a good chance of knocking off Greens' incumbent Scott Ludlam.
"Wirra" is getting some help from preferences such as the WikiLeaks Party favouring him ahead of the Greens, despite Senator Ludlam being the most vocal politician to support founder Julian Assange.
Palmer United Party's Dio Wang has a chance to sneak in thanks to a strategy of harvesting preferences from micro-parties.
In South Australia, Greens immigration spokeswoman Sarah Hanson-Young faces defeat at the hands of the Liberals or popular independent Nick Xenophon's running mate Stirling Griff.
In Queensland, maverick MP Bob Katter's Australian Party and mining mogul Clive Palmer's Palmer United Party are in a high-profile fight to win a seat.
Both have got celebrity candidates - country musician James Blundell for KAP and rugby league great Glenn Lazarus for PUP. Mr Blundell will get a boost from Labor preferences, while PUP is polling strongly with 6 per cent of the vote, according to the latest 7 News/ReachTel poll.
Despite the trend running towards the coalition, the Liberals fear highly regarded NSW Senator Arthur Sinodinos could be ousted by Pauline Hanson.
Ms Hanson has tried countless times to re-enter politics after being defeated in 1998 and has come close, only being thwarted by the major parties not preferencing her.
This time she has the benefit of standing under her original One Nation banner.
A record 529 Senate candidates are running nationwide, complicating the already difficult task of calculating winners.
Although Labor and Greens will retain control of the Upper House until July, when the new Senate sits, the coalition is expected to have 36 senators, three short of a majority.With Senator Xenophon to hold his seat and the Democratic Labour Party's John Madigan only halfway through his six-year term, an additional conservative crossbencher such as Mr Blundell or Mr Lazarus could make it easier for Mr Abbott to negotiate legislation.