Nearly half of voters - 46.7 per cent - say they have a lower opinion of Banks after his statements of the past week on local government election donations.
The telephone survey of 510 eligible voters in the Epsom electorate aged 18+ has a margin of error of +/- 4.34 per cent.
Political pundit site iPredict has Banks little better than a 50:50 chance of still being a Cabinet minister by Budget Day on May 24.
Left-wing commentator Matt McCarten, in today's Herald on Sunday, raises an interesting scenario - that an early Banks resignation would advantage National at an Epsom by-election. National would win and get an extra MP on top of existing numbers, bolstering numbers in the house by one, reducing the need to negotiate with Act and opening up a Cabinet position for one of its own.
However, the Herald on Sunday-Key Research also has concerning results for Prime Minister John Key.
Asked whether an endorsement from Key would affect a decision to vote for Banks or Act, almost three-quarters of respondents said it would not. An endorsement from Key has been seen as crucial to the fortunes of Act Party candidates in Epsom at past elections.
Other potential opponents also smell blood in Epsom. Conservative Party leader Colin Craig said on TV3's The Nation it was highly likely he would stand in Epsom if a by-election was called.
"Obviously that's a board decision, but I am confident I would get the nod."
- Edward Rooney
Caught in the Act
A fresh battlefield has opened up for Act Party leader John Banks.
Concerns have been raised surrounding the appointment of a former party colleague to lead the charter schools trial.
Former Act president Catherine Isaac was appointed to chair the board overseeing the trial of charter schools, but a Ministry of Education report, released under the Official Information Act, shows Banks announced his intention for Isaac to be appointed as far back as January. Cabinet established the working group only on March 7 and Isaac's position on the working party was made public on March 28.
The report indicates Isaac met officials on February 3 to talk about setting up the group.
In a statement from Banks' office this week, he said the appointment was appropriate but he did not answer questions on the process.
Green MP Catherine Delahunty said Banks obviously decided he wanted his Act colleague in charge no matter what, which had undermined the credibility of the group's leadership and showed "it was about implementing Act agendas rather than improving our education system".
Labour MP Nanaia Mahuta said, "I don't doubt Issac's skills but cronyism comes to mind".
A spokesman for the chair of the appointments committee, Prime Minister John Key, said: "The Prime Minister is satisfied the appointment was handled in an appropriate manner."
- Chloe Johnson