Earlier today I criticised Labour for following the usual "keeping your powder dry" strategy of not announcing specifics in their announcement that they were abandoning the NeoLiberal consensus on monetary policy. I focused on the principle - that the strategy is dishonest, puts power before policy, and treats the public like children. But there's another reason for parties not to use it: its counterproductive.
Just look at what happened today. Phil Goff announced his policy, but didn't give specifics - which gave National's spindoctors the chance to just make something up. And so Goff was forced to defend himself on the six o'clock news against allegations he planned to levy mortgages and increase petrol prices, policies he had never advocated.
If you announce a policy with details, you have to defend it. If you announce without details, you have to defend not just your actual policy, but all the other policies your opponents say you have as well. You buy into a pile of extra trouble, and all for the dubious and unlikely "benefit" of not being able to get the government to do the dirty work for you (or, to put it another way, of not being able to exercise power from opposition - which is a pretty impressive feat in my book).
That equation just doesn't make sense to me. Better to be upfront with the public instead. After all, what's the worst that could happen? They could lose an argument? If so, then it is better to do it now, when policy can be corrected, rather than in the heat of an election campaign when the loss matters.