Tasmanian senator Jacqui Lambie is at risk of losing her seat, with vote counting for the state's final Senate positions remaining tight.
She's facing competition from One Nation's Lee Hanson, daughter of party leader Pauline Hanson, for the sixth and final seat.
But the final spot could also be won by Labor, which secured a more than 8 per cent swing in Tasmania.
As of Tuesday morning, 62.9 per cent of the vote had been counted, with two of the six Tasmanian Senate seats still in doubt.
Labor's Carol Brown and Richard Dowling, the Liberals' Claire Chandler and the Greens' Nick McKim have secured the first four seats.
The Liberals' Richard Colbeck is vying for the fifth or sixth spot.
While One Nation is seen as a potential threat, the Jacqui Lambie Network is currently ahead with 17,273 votes to One Nation's 12,949.
Candidates need 35,071 votes to secure a Senate seat.
Lambie's party is seeing a -1.6 per cent swing, while Hanson's is up 1.39 per cent.
The ABC's chief election analyst Antony Green said the likely outcome is "no change — two Labor, two Liberal, one Greens — with Jacqui Lambie in a race for a seat with the third Labor candidate".
A three-way race
Shaun Ratcliff, principal at social and political research firm Accent Research, says the seat is a "three-way race" — and One Nation isn't in it.
"Jacqui Lambie looks like she has a pretty good shot at one of those last two spots," he told SBS News. "But I think it's Labor, Liberal and Jacqui Lambie — it's not One Nation."
But due to preference flows, the result remains hard to call.
"There's not a lot of daylight between the Liberals' second spot, Labor's third spot, and Jacqui — they're all pretty close," Ratcliff said. "If one of them got really strong preference flows, it gets them over the line for the fifth or sixth spot."
"I wouldn't feel confident if I were any of those three. It's close enough that it could go anywhere."
Ratcliff said the result may not be known for weeks, until the Australian Electoral Commission finishes its official count.
Simon Welsh, director of political research and polling firm Redbridge Group, said Lambie could benefit from preference flows from minor parties.
"Your gut feel would be that all those crazy minor [parties] would probably land on a Jacqui Lambie before they land on a Labor or a major party," he said.
While much is still up in the air, one outcome seems increasingly unlikely.
"The only thing I'd be reasonably confident on is that it seems really unlikely that One Nation gets a spot from that far behind," Ratcliff said.
What the broader Senate will look like
Nationally, Labor is on track to win 28 Senate seats, the Coalition 26, and the Greens 11, with the remaining spots going to crossbenchers.
"Labor looks set to gain three seats at the expense of the Coalition, which will aid the passage of legislation," Green said.
To pass laws, the government needs 39 Senate votes. If these results hold, Labor would only need the support of the Greens to pass its agenda through parliament.
