Trying to persuade people of things they don't already believe is far harder than persuading us our prejudices are incorrect.
There isn't much choice for Phil Goff, so this week he listed John Key's record:
The economy has grown only 0.4 per cent since he took office; unemployment is up by half; prices went up four times faster than wages; one hundred thousand of us have gone to Australia because wage packets there have grown another $32 fatter than ours since John Key took office.
Labour risks making the election a referendum on the Government's time in office, and voters believe National has done OK. But it's valid to ask what National has done to improve any of those dismal scores. A cycle lane is not exactly game changing.
The other way Labour is trying to dent National's "more of the same" complacency is by highlighting long-term risks. We have a national borrowing habit, our industries are too narrowly based, and we need to make retirement more affordable.
So they've ended up highlighting policies that are not exactly populist, including a capital gains tax and increasing the retirement age. Change is inevitable, so we might as well begin.
But change is also a risk, which is why voters are rewarding a government that is cautious and conservative in tough times.
John Key sought to highlight the risk of change last week in the Press internet debate, with the "show me the money" line that has become notorious.
His assertion of a giant hole in Labour's books has been widely repeated. But his accusation of a $17 billion hole was based on thin air, and if it turns a single vote it will be a travesty.
Mr Key informed us he was sure of this figure because he has spent his life working in finance. Yet today, there is not an expert anywhere who believes the claim of a $17 billion hole stacks up. Even the National Party has abandoned the figure.
Mr Key was implying a huge spending gap exists in Labour's alternative, when he knew that was never true.
It wasn't a bad day's work: A week of headlines suggesting Labour had done its sums wrong, based on an attack that was not only wrong, but which the Prime Minister knew to be wrong.
The more risk he can associate with Labour, the less appealing he can make "change". Drift got us through the last three years, but not very far. If National is re-elected, nothing will change.
John Pagani is a former adviser to Labour leader Phil Goff and former Progressives MP Jim Anderton. He blogs at johnpagani.posterous.com.