Act leader Rodney Hide has the votes to fend off a takeover bid by former National leader Don Brash, the party's president has claimed.
Dr Brash last week confirmed he wants to helm Act and threatened to bleed the party of votes if it did not accept him as its leader for the November general election.
He needs the support of at least three of Act's five sitting MPs for his bid to be successful.
MPs Roger Douglas and former deputy leader Heather Roy are expected to vote for the takeover.
But MPs John Boscawen and Hillary Calvert had given "firm" assurances of support for Rodney Hide, Act president Chris Simmons told Radio New Zealand this morning.
It was unclear how Dr Brash expected to carry out the leadership coup, he said.
"John's been very supportive of Rodney. Both men want the best for the party... Hillary Calvert's told me she's 100 per cent behind Rodney as well.
"Right now I'm seeing three very firm votes on this from caucus."
Mr Simmons said the Act board would support Dr Brash for leader if it was recommended by the party's MPs in order to avoid a "constitutional nightmare".
But he said Dr Brash's plan for former Auckland Mayor John Banks to stand as a candidate in the Epsom electorate was "unpalatable".
He also criticised him for playing out the leadership stoush in public and said he did not see how he could lead a party when he had not become a member.
"This appears to be a takeover. Don has put down that he would like to see John Banks stand in Epsom. That's just unpalatable. I can't imagine how this will actually play out."
Key prepared to work with Brash
Prime Minister John Key earlier refused to rule out working with a party led by Dr Brash.
But he said speculation about how National would work with any new political movement is premature.
"I think we're a number of steps ahead of ourselves.
"At the end of the day we as a political party will work with what the electorate delivers."
He said National had a good working relationship with Act under the leadership of Rodney Hide.
Dr Brash has commissioned a nationwide poll to gauge the level of support for him as leader of Act versus Act under incumbent leader Rodney Hide.
He expects the results next week, after the Act board meeting.
"I'd like to say to the board that, under my leadership, I believe Act has a much better prospect of not only getting back into Parliament but having a significant number of MPs."
He will also point out that a new party, which he will set up if his bid to roll Mr Hide fails, could seal Act's fate by taking a bite out of its voting base.
When asked if that could be seen as a threat, Dr Brash said: "I don't want to put it in that way but I am deeply concerned about where the country is and if I can't make a contribution in the Act Party, I'll find some alternative way of doing so."
His preferred approach would be as leader of Act, he said.
"The party's already established, it has a constitution, a membership ... It's got all those things that are easier to take over than to try and create from scratch. I don't doubt I could do it but it would just be much more convenient to assume the leadership of Act."
Mr Banks has not ruled out standing in Epsom.
He said Epsom and Mr Hide had "parted company". But when asked if he would like to represent Epsom one day, he sidestepped the question saying: "They're a great bunch, the people of Epsom."
Mr Hide has said Dr Brash's bid is a takeover attempt by a member of a different party.
Confident of keeping his leadership, he said if Dr Brash wanted to become leader, he would have to follow the process and first become a member of the party.
Right-wing political commentator Matthew Hooton does not expect Act to take up Dr Brash's offer - even though he believes it is the party's only chance of survival.
"Act is a cult of Rodney Hide acolytes," he said. "I think they'd all prefer to commit political suicide than take this opportunity. And if they don't take it, the new [Brash-led party] will be more successful than Act."
According to the party constitution, the caucus can recommend a new leader by majority.
The board must accept the caucus' choice unless at least eight board members vote to overturn it.
Dr Brash needs three votes from the caucus and the support of at least five board members to block a vote of eight or more against the caucus recommendation.
There are normally 13 board members but the Waikato/Bay of Plenty seat is vacant.