The public is being urged to show politicians that they want a national, covered, multi-purpose stadium on Auckland's waterfront.
The consortium behind The Crater Arena Aotearoa project has taken out advertisements aimed at prompting people to support The Crater on a poll at change.org.
Their design - a see-through enclosed structure that could scale for crowds from 20,000 to 70,000 - is a finalist in the future projects category of the World Architecture Festival Awards.
But the stadium, which would be sunk into the Waitematā Harbour next to Bledisloe Wharf, needs positive support from politicians to give private funders the confidence to fork out for a detailed feasibility study.
If public support is strong enough, politicians will listen, consortium spokesman Michael Sage told the Herald On Sunday. With local body elections pending, it was a good time to push for that, he said.
The consortium had already spent $2 million of its own money and estimated the feasibility study would cost about $15m, money that would be repaid by the developer if it went ahead.
The stadium itself would cost $2 billion to build but none of that would come from taxes or rates, Sage said.
The project would require Bledisloe Wharf - currently used to park imported cars - to be freed up, and for Eden Park to be scrapped, with both blocks of land being given to the chosen construction firm to develop in exchange for it footing the cost of building the stadium.
Sage, a partner specialising in infrastructure with law firm Simpson Grierson, said the chance to build an iconic enclosed stadium without a hit on the public purse was a chance that came up only once in many generations.
"It takes some time for politicians to get behind it. That's why it's so important to show them there is public support for it."
Legislation will be needed to alter the Port Companies Act which limits the council's authority over the port.
Sage said Auckland needed a stadium like The Crater now and it would be "desperately needed" in 10 years time "when Eden Park will be on its last legs and Mt Smart stadium will be gone".
Forsyth Barr Stadium in Dunedin is New Zealand's largest and most versatile indoor events arena. That was controversial at the concept stage but had been embraced, Sage noted.
Commenting last year on the vision, the Herald's Auckland affairs writer Simon Wilson said the sunken stadium proposal had "already sharpened debate on what should happen on the site, and to Eden Park and other sports venues, in a way we haven't seen for a long time".
Auckland Council plans to look at the stadium issue in 2021, when it refreshes the 10-year-budget.
Mayor Phil Goff last month told the Herald he favoured a city site but the cost of over $1.5b was prohibitive and not a priority ahead of transport, housing and the environment, which would mean Eden Park would remain as Auckland's international stadium for at least a decade.
Mayoral candidate John Tamihere wants to upgrade Eden Park to become a multi-event venue, including for concerts.
AUCKLAND'S ON-GOING STADIUM SAGA
• Government offers to build a waterfront stadium in 2006 for the 2011 Rugby World Cup.
• The plan doesn't go ahead and Eden Park is instead redeveloped with a $256m upgrade to make it the tournament's centrepiece.
• The debate flares up again in 2016 after officials questioned the future of Eden Park and Mayor Phil Goff pushes the railway site in his successful mayoral campaign.
• Goff cites $250m would need to be spent on Eden Park over the next 15 years to maintain it.
• Meanwhile debate rages over how to use the city's other stadiums - notably North Harbour Stadium, Western Springs and Mt Smart - and how sports should be catered for.