The Opposition parties just have to keep searching for the right question They have asked him whether his staff have ever provided "inappropriate services" for the National Party. They have asked him about his conversations - spoken or text - with Cameron Slater. They have asked him whether he is satisfied his office has upheld the highest ethical standards.
They - Labour, the Greens and New Zealand First - have asked John Key a lot of questions concerning Nicky Hager's Dirty Politics since Parliament resumed sitting last week.
The book may have been released before September's election. There is ample material, however, for Opposition parties to probe post-election what Key did or did not know about dirty-tricks operations being run out of an office on his floor of the Beehive.
The ultimate prize would be to get Key's reputation tarred for good. So far, however, the Opposition's daily quota of questions has yet to trawl up a reply which offers even a smidgen of proof of those parties' suspicion that Key knew what was going on. Naturally, Key is not going to allow his opponents free rein to tie him to the rack in some modern day version of the Spanish Inquisition.
Yesterday was a case in point. Greens co-leader Russel Norman asked the Prime Minister whether his chief of staff, Wayne Eagleson, had approved of Jason Ede, then on the Prime Minister's staff, hacking into the Labour Party's private database.
Key replied no, but added that Ede had accessed parts of Labour's website that had not been blocked.
Norman then pondered whether the PM was saying that if he left the door open to his Parnell home and someone walked in, wandered around, and took some stuff without his permission that would not be stealing.
Key ducked the question and instead went on the attack.
"If the member wants to talk about stealing, let us talk about Nicky Hager and where he got his emails from."
Key may be hard to pin down. But the Opposition parties just have to keep searching for the right question which forces Key to provide an answer he does not want to give.
The worry for those parties is that if there is such a question, they should have come up with it by now.
Targeting Labour during a later debate, National's Steven Joyce was reminded of Albert Einstein's definition of insanity: doing the same thing again and again, but expecting a different result.
Indeed, the Opposition parties may be asking themselves whether they are indulging in something mad.
Their seeming lack of co-ordination and the consequent haphazard nature of their attack on Key's credibility leaves open the question of just how committed those parties are to the offensive - and for how long.