I think the reason is because the public are not convinced Phil Goff and Labour believe in them themselves. This is hugely important to voters. They will vote for a party if they believe the party is sincere and believes in its policies - even if they themselves do not agree with them all. This is how John Howard got re-elected in Australia despite massive opposition to his stances on Iraq and boat people. They respected Howard as believing in what he promoted and he got a fourth (but not a fifth) term.
Phil Goff ruled out a rise in the age of superannuation eligibility in July this year. So when you then announce it as policy three months later, the public don't think you sincerely believe in it. Otherwise why did you rule it out 90 days earlier? And when you claim it as proof you are a bold leader, they again are sceptical. They conclude (probably correctly) that the policy was adopted purely to position Goff as a "bold leader" rather than a sincere belief that it is better to increase the age of eligibility, than to increase taxes in future to pay for the extra cost.
The same argument applies with Labour's capital gains tax. Phil Goff dismissed one earlier this parliamentary term.
Now some may say what about John Key on GST. Did he not change his position? Well, yes he did. And I would never argue that MPs should never change a position. But Key's change of stance was on the back of an independent report that recommended reducing income tax and lifting GST so that there are greater incentives to work and save. That allowed the public to understand the change of stance (if they had not, then Key would not have remained so popular).
So if you change you policies and your position, especially from just three months earlier, you need to make the case for why you have changed your stance.
The same applies to Labour's stance on the Government's books. Labour spent two and a half year attacking every single decision the Government took to reduce spending to get New Zealand out of the projected permanent deficit that Treasury projected at the end of 2008. They not only opposed every spending cut that the Government made, they actually argued that the Government should be spending massively more like Obama did. Right up until 2011 they were arguing that it was more important to borrow and spend to (temporarily) boost the domestic economy than to keep a lid on spending.
Then a few months ago, they realised that the voters were becoming very worried about debt, in light of the on-going troubles in Europe, and suddenly Labour stopped arguing that the Government should spend more, and said that they would spend and borrow pretty much the same as National was.
Labour's problem again, is whether voters will believe them. It doesn't really matter that much what numbers they announce today as their fiscal plan. The bigger issue is whether voters actually believe that the current Labour caucus really believes in spending restraint, when they have spent two and a half years arguing against it at every opportunity.
Labour may have been better to stick to its original position of saying "Yes we will spend and borrow more, because that will get people back into jobs and that is more important than debt". It's not a position I personally agree with, but it is a position which I think most of the Labour caucus actually believe in their hearts.
*David Farrar is a centre-right blogger and affiliated with the National Party. A disclosure statement on his political views can be found here.