A right-leaning political commentator believes the pressure on John Banks to quit was Jamie Whyte asserting himself over some of the old guard in the Act Party.
Lobbyist Matthew Hooton says he understands Act's leader essentially said to Banks that he should resign in the interests of the party and integrity of Parliament and if he didn't the decision would be made for him by the party.
Media coverage showing the initial response by some in Act to defend Banks prompted Mr Whyte to determine that it was not going to work and they had to "get rid of this guy", Mr Hooton believes.
While believing Banks may have a role in the future as an advisor, Mr Hooton told TVNZ's Breakfast this morning that there is a generational change going on in New Zealand politics and within the Act Party.
"It's time for the newer generation to assert itself."
Mr Hooton also believes Mr Whyte has to bring campaign director Richard Prebble under control while retaining his skills.
And he says it's a fact of the polls that John Key can't get a third term without Act.
"Act must win Epsom or else David Cunliffe becomes prime minister."
Mr Key is going to want Mr Whyte and Act's Epsom candidate David Seymour to "stop talking about this nonsense and start talking about the things that will appeal to the high tax voters of Epsom".
Mr Key told Breakfast he thinks National can win the next election without Act but he believes Epsom voters want National to be in Government.
"MMP drives coalitions, you need partners, in the end there'll be coalitions formed."
The Prime Minister says it was quite clear to Banks that he would have to resign and the question then became a timing issue.
"He wants to go away and work on clearing his name, he's got potential appeal processes he can go through," Mr Key says.