Worse, the details of the "teapot" conversation are so embarrassing to Key and Banks that the investigation inevitably looks as if it is trying to spare them from embarrassment.
That is unacceptable at any time. Less than 10 days out from an election, it is deplorable.
Potentially troublesome for National, however, is that so besotted has Key become with media ethics that the election is fast becoming a simple equation. Has enough support swung in behind the Prime Minister for his taking a stand on privacy rights?
Or will the emerging detail of what was discussed by Key and Banks push New Zealand First over the 5 per cent threshold and give Winston Peters enough seats in Parliament to make it difficult for Key to form and run an effective Government?
Those springing to Key's defence need reminding that politics is a numbers game at the end of the day. That is the political bottom-line in all this. The finding in today's Herald-DigiPoll survey that New Zealand First is registering at 4.9 per cent should therefore send shudders through National.
Last night's 3 News poll also showed Peters' party slowly picking up support.
These polls put Peters in the perfect position going into the last week of the campaign pushing an issue that is tailor-made for him.
It is still a very long way from happening, but Key's blundering may just conceivably see him having single-handedly helped his nemesis back to Parliament - and tossed National out of power.
What is not in question is that Key's hopes of toughing it out and the whole business losing steam has proved to be wrong. The police investigation means this will run and run until election day.
SIDELIGHTS
Damn the dams: Labour's TV ad warning that selling a portion of the state-owned electricity generators will mean higher power prices has prompted a complaint to the Broadcasting Standards Authority over the phrase, "Wait until you don't own a damn thing", and whether that is a profanity.
They said it:
"I'll be keen to find out." - Don Brash when told John Key and John Banks had secretly discussed the dumping of Brash as Act's leader and give him an overseas diplomatic post.
"The whole thing is a circus and that is what happens at a circus: someone falls off the elephant. - Winston Peters' unique take on the "teapot tape" affair.