Tasmania's upper house will on Wednesday begin debate on an order to approve a $1.13 billion 23,000-seat roofed venue at Macquarie Point in Hobart.
The stadium, backed by the state's two major parties, is a condition of the Tasmania Devils joining the AFL and AFLW in 2028.
The project sailed through the lower house in November and needs the votes of at least eight of 15 upper house members to get the green light.
Key independent Bec Thomas on Wednesday morning said she would vote for the project after securing concessions from the state government.
"I have given my support to this project to the government conditional on their agreement to a range of safeguards," she told ABC radio.
Fellow independents Tania Rattray and Casey Hiscutt have yet to declare how they will vote but have previously spoken in favour of a stadium - which would give it the numbers to pass.
Ms Thomas, a former mayor, said the decision was one of the hardest she has ever had to make.
One of the safeguards include a fixed cost cap on the state's contribution of $875 million.
The AFL is contributing $15 million to the stadium and the federal government $240 million, with Tasmania paying $375 million plus the remainder in borrowings.
Ms Thomas also said the government had agreed to consider funding sporting facilities, including in Hobart's north in her electorate.
An estimated 15,000 people rallied in support of the stadium on Sunday, after 1500 attended an anti-stadium protest a week earlier, although the official police figures have been disputed.
Tasmania's planning authority recommended the stadium not go ahead, saying it was too big for the site and its costs outweighed its benefits.
The state's debt is set to more than double to more than $10 billion in 2028/29, while the stadium has blown out from an initial $715 million.
Premier Jeremy Rockliff, who inked the AFL contract, on Tuesday admitted he was nervous about the outcome.
He told the pro-stadium rally the upper house vote would define the state for generations.
"The Tasmanian Devils and (our) aspiration for young people has brought it to this point. We're going to get the job done," he said.
Mr Rockliff has trumpeted the venue as transformational, an economic driver and the only chance to guarantee Tasmania's long-desired entry into the AFL.
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