If politicians learn one thing from this sorry Parliament it must surely be not to make promises they can't keep.
You'd think they'd have figured this out after Bob Hawke's 1987 campaign launch promise that by 1990 no Australian child would need to live in poverty, an impossible pledge he has said is one of his biggest regrets.
But since 2010 the government has proved that rash promises - far from reassuring and convincing voters - can disastrously distract from the merits of what it has been doing.
Julia Gillard's broken promise that there would be ''no carbon tax under a government I lead'' has helped undermine her legitimacy and authority as leader and the sensible policy rationale of the carbon price she succeeded in introducing.
It was made when she was still saying she would introduce an emissions trading scheme at some stage, which she must have known was likely to start with a fixed price, that is, a tax.
And when in 2010 Treasury projected the budget would be back in surplus by 2012-13, the Gillard government rashly turned that projection into a ''come hell or high water'' guarantee, repeated with increasing forcefulness over the ensuing 2½ years (the Coalition can provide the full quotes list, in fact it tweeted most of them on Thursday).
Given that Treasury projections are just that - projections - and often end up being wrong, or buffeted by unforeseen events, it was crazy not to add some kind of caveat.
Tony Abbott and Joe Hockey are perfectly justified to hold Labor to account for this. Yes, revenue did not meet Treasury's projections. Yes, the government did absolutely the right thing to concede it would be counter-productive to still try to achieve the surplus with the economy slowing and revenue falling. And possibly they could have spent less on stimulus during the financial crisis or cut spending more in the budgets delivered since. But as things stand, trying to deliver a surplus next year would be a destructive triumph of politics over good economic management.
But voters are entitled to be cynical, especially since senior ministers kept repeating the ''Labor will achieve a surplus'' script even when everyone knew it was nonsense and right up to the point when Wayne Swan's announcement delivered them with a new one. And that cynicism clouds the economic arguments that support the decision the government has made.
(Changing script has been a problem for Labor historically. Remember when the global financial crisis hit and Labor couldn't even say the word ''deficit'' - leading to this ludicrous November 2008 7.30 Report exchange.
Kerry O'Brien: Will you accept going into deficit, if you have to, to maintain appropriate stimulus of the economy under the threat of recession and high unemployment?
Wayne Swan: Kerry, it would be silly to speculate along the lines of your question.
Kerry O'Brien: Why?
Wayne Swan: Because I've made it clear. We are projecting modest growth and modest surpluses but if the situation were to deteriorate significantly, it would have an impact on our surpluses and it may well be the case that we could end up in the area that you're speculating about.
Kerry O'Brien: Well, say it. In a deficit.
Wayne Swan: I am not going to say it, because we're projecting modest surpluses Kerry.
Two weeks later then Prime Minister Kevin Rudd finally said the ''d'' word.
So scared was Labor of the political ramifications of running a deficit that it prefaced every mention of ''deficit'' with the word ''temporary''. And that's why it seized on Treasury's 2010 forecast for a surplus in 2012-13, which is how it ended up in such a bind.)
But this week's decision might just free us up to have a sensible economic and policy debate in the lead-up to next year's election.
Instead of fiddling around looking for tricky ways to create the illusion of a surplus, Labor can concentrate on how it intends to encourage growth, protect employment and pay for the promises it has made on education in response to the Gonski Review and the introduction of a national disability insurance scheme.
And instead of taking the Annie Oakley approach (anything you can do I can do better) by promising bigger surpluses than Labor come what may, the Coalition can simply calculate the budget position it will be in after all the spending and saving policies it will unveil in an election year.
To be fair, Joe Hockey has been careful to say that the Coalition's surplus promise was ''based on current forecasts''. And it now seems more likely that forecasts for future financial years, when a Coalition Government would be delivering budgets, will also be revised. That means his sensible caveats might end up coming in handy.
Which brings us to two promises made in the dying days of 2012 which politicians should be absolutely held to in 2013.
The first was from Julia Gillard.
In one of her final interviews for the year with the ABC's Sabra Lane, the Prime Minister said the Australian people would ''see from us every cent for Gonski and the National Disability Insurance Scheme over the forward estimates and they'll see more than that. They'll see us detail a long-term funding strategy. We will be absolutely transparent with the Australian people. Budget forecasts properly done, Treasury forecasts, all the rest of it, every dollar, every cent and a long-term funding strategy.''
The promise of a major long-term funding strategy is a huge one, since the disability reforms will cost at least $8 billion a year when fully running and the Gonski reforms ramp up to an annual cost of $6.5 billion.
The second promise was from Joe Hockey, who said this, as he explained that the Coalition's surplus promise was ''based on current forecasts''.
''We are not going to deliver overblown rhetoric and set benchmarks that cannot be met,'' he said.
A very Merry Christmas to that.