He predicted that the campaign so far, including the Dirty Politics book and stunts such as burning effigies would keep voters out of the polling booths.
Speaking to media afterwards, he repeated his belief that New Zealanders were more interested in the economy than politicking after taking numerous questions on the Dirty Politics book and the involvement of National minister Judith Collins, his own staffer Jason Ede and others.
The Green Party has claimed its economic policies would pay down debt faster and get bigger surpluses, than under National. Mr Key said he knew the Greens were also keen on legalising cannabis.
"If they really believe that, maybe they've been trying the substance because they can't do it." Asked if he thought Dr Norman had been smoking weed when he put out the numbers, Mr Key said "well, if he really believes those press releases, yes. Press releases are cheap and easy. Getting back into surplus is a much more challenging issue."
Mr Key said between them Labour and the Greens had made $28 billion worth of promises already. Even if Labour stuck to its promise to remain in surplus, it would leave no buffer if there was another disaster that impacted on the economy.
"These are people that will send New Zealand back into a significant deficit and I think New Zealanders are very worried about that."
Mr Key is in the Wairarapa helping local candidate Alistair Scott campaign.
NZ First has just selected Carterton Mayor Ron Mark as its candidate. Mr Key said he was not concerned that would split the vote. Mr Mark is seen as friendly toward National, and Mr Key said while it could help in any future talks he still preferred his current support partners over NZ First.
Mr Mark was on the invite list to the Chamber of Commerce lunch but did not show up.
National's campaign ads feature the Greens and Labour in a boat trying to row in opposite directions, and Mr Key said it showed voters had a choice between "plain sailing" under National or "a group of parties that will be causing chaos and you wouldn't want to be at sea with."
Asked where Act's cabbage boat was he said "no chance of that."
He had earlier reinforced to the audience at the Chamber of Commerce that National would struggle to get a majority and it needed its voters to turn out.
Green co leader Russel Norman said he stuck by the Greens' claims and the numbers in its alternative budget were accurate.
He said they had been independently verified by Infometrics.
"John Key should stick to his own advice of focusing on policy, rather than making totally untrue and defamatory personal attacks."
