There's been a shift in the balance of power on the Hawke's Bay Regional Council, with the majority now not in complete favour of the Ruataniwha water storage project.
Five of the nine elected councillors have said they oppose the dam or have major questions about it.
The regional council has yet to decide whether to go ahead with the project, and the $900 million scheme also faces legal hurdles.
The council wants to dam 22ha of formerly-protected land, flood it and give the department 170ha of nearby farmland in return.
The Court of Appeal has ruled the process of acquiring the protected conservation land was unlawful and ordered the Director-General of Conservation to reconsider his decision on the land swap.
The Department of Conservation and the council have jointly sought leave to challenge that ruling in the Supreme Court.
Now, dam critics Rick Barker, Tom Belford, Rex Graham and Peter Beaven have all been re-elected.
They will be joined by new councillor Paul Bailey, who is an anti-dam campaigner.
Mr Bailey said voters had given councillors the mandate to stop the dam going any further.
"To my mind it's an absolute game changer," he said.
Mr Bailey said he wanted to find out how much it would cost to cancel current dam-related contracts.
He also expected the current council chairman, Fenton Wilson, to be replaced.
Another newly elected councillor, former New Zealand First and independent MP Neil Kirton, said there should be a moratorium on the dam until the council has its ducks in a row.