New Zealanders instinctively trust John Key as a straight-shooter. But at what point do voters start to see the Prime Minister as tarnished by the Dotcom spying affair?

Trust is one of the most valuable political currencies; if the public puts their confidence in you, politicians can achieve so much more, feel much safer in their jobs and demand more loyalty from your colleagues. John Key, such a successful trader of actual currency, has also proven to be astute at accumulating its political equivalent. But these days he seems to be spending more than he's saving and the question is when those savings will run out.

Thus far, his trust account, as it were, looks as healthy as ever. The latest polls show him still in a strikingly strong position as preferred Prime Minister, far and away the dominant figure in New Zealand politics. National is riding his coat tails, as it has been for years.

Voters have instinctively liked and trusted him for a long time, and don't seem inclined to re-think that impression in a hurry.

But the Dotcom saga has been eroding that trust and took another withdrawal this week, with Key's admission that he rang his old family acquaintance, Ian Fletcher, and suggested he might like to apply for the job leading the GCSB; a job that reports directly and only to Key as Prime Minister.

I've no problem with the fact Key and Fletcher knew each other as children and now work together. We're a small country with small talent pools and it's inevitable people of ability will become both friends and colleagues.

I've little problem with Key suggesting contacts for senior roles in the public sector. While any Prime Minister must be careful not to be seen to be compelling any appointments or playing favourites, there's no reason he can't chip in with the odd name.

I've a little more of a problem that he made the phone call directly to Fletcher, as it once again shows a looseness and lack of respect for proper process. As I wrote back in March and in February, Key cares about results, not about how you get there. And in government, that's a concern because the means should matter as much as the ends.

And it's a concern that attitude may be catching. State Services Commissioner Iain Rennie on Campbell Live last night defended the process of hiring Fletcher by insisting it was OK because Fletcher was doing a good job. Now that's debatable, given the handling of the Dotcom spying. But then Rennie went on to say:

"I'm still driven by the outcome".

That struck a worrying chord with me. A State Services Commissioner, more than just about anyone, should care about means as much as ends.

Still, the biggest problem for me in this week's developments is not the inappropriate hiring methods per se, but the Prime Minister's lack of full disclosure. Last week, when asked what role he played in Fletcher's appointment, Key said:

"Only that the State Services Commissioner came to me with a recommendation."

And the next day:

"I didn't undertake the recruitment, that was fully done by the State Services Commission."

Those statements were clearly false, given we now know Key made the phone call that made Fletcher aware of the vacancy. So this week he admitted:

"I rang him and said look I think you might be interested, if you are interested in finding out about the job you should go and speak to Maarten Wevers who is the head of DPMC and see if that job is of interest to you."

So voters are left to decide whether Key was hiding the truth last week or had genuinely forgotten.

Either way, that must amount to a debit to his trust account. The occasional memory lapse is human, but six high profile ones suggest either convenient and dubious excuses or a lack of attention. Either way, voters will start to wonder just how reliable the Prime Minister is.

It does stretch credibility to accept that Key could recall his family's relationship with Fletcher's, presumably discuss the political implications with his staff and be questioned at length by reporters about that relationship and his role in the appointment and simply forget that he kicked the appointment off with the phone call.

So the problem becomes not the phone call itself, but the resulting excuses. And just how uncomfortable he looked on camera.

As I pondered Key's trustworthiness this week, I remembered Kim Dotcom's assertion last year that Key has lied as to when he knew about Dotcom. Dotcom insisted he would prove Key a liar and said:

"[John Key] is running naked and telling people he has clothes on. Everyone can see he's naked."

The polls tell us that voters have a different view of Key. The question is for how much longer, as he seems to be a little less well dressed – a little less trustworthy – than he did a week ago.