There's a lot of upside down politics in the Solid Energy saga, but at the end of the tunnel it's all about the next election

"Show me the money", John Key hooted at Phil Goff in the 2011 election campaign, painting Labour as a party of loose financial discipline. Can you trust a party that doesn't know how to get out of deficit, wants to tinker with vege taxes and create tax-free zones, he asked voters. And they said no.

While some in and around Labour don't think the leaders of that woeful campaign have taken sufficient accountability or looked hard enough at its failings, as Charles Chauvel said in his valedictory speech, Labour at least understands that a lack of economic credibility has hurt its electoral hopes. The tax-free zone was quickly jettisoned and restoring payments to the Super Fund became a lot less urgent, for example.

And economic credibility is what the battle over Sold Energy is now all about. Labour is running this hard because it sees a chance to place a seed of doubt in voters' minds about National's economic cred.

After the appearance before the select committee by Don Elder and John Palmer, it's clear that the company was ambitious and focused on growth. However to achieve that growth it took on more debt than it felt comfortable with, due to government urging. The record is clear that National was happy with SOEs borrowing more and that they were especially big fans of its plans for lignite development in Southland.

Now that debt which National was so keen on has left Solid Energy horribly exposed as the price of coal has dived in the past year. Labour's message to voters: National's so called economic cred isn't worth the paper it's written on. The hope is that if it can't reach surplus in the next 18 months it has a couple of very big sticks to whack National with come the 2014 election campaign.

Of course this story is rich in political hypocrisy. Through the prism of Solid Energy, you can see National encouraging SOEs to take on more debt, while being incredibly conservative towards and protective of its own balance sheet. Debt? Bill English and others in government have warned repeatedly of its dangers and spoken in almost religious tones of the importance of returning to surplus, all the while nudging SOEs in the opposite direction.

Debt? Why not? It was classic 'do as I say, not as I do'. Now, with not a rain cloud in sight, National is left with the challenge of making those losses up somehow in the next year or so if it wants to achieve its holy grail of surplus.

But it goes both ways. Labour's criticism of National in this case is essentially that it was too 'hands on' and too relaxed about debt. This from the party that is usually saying National isn't hands on enough and is happy to carry a bit more debt on its own books.

None of that really matters much to voters, however. Despite protestations to the contrary by Palmer and Elder, the public sees a company that hadn't covered its backside or prepared itself for a stormy day. They see millions of taxpayers' dollars gone and the need to blame someone. And they see a government that's preached the evils of debt caught out by that very evil.

It will take more than this to dent the personal credibility of John Key in the eyes of middle New Zealand. Many will accpet that there's only so much a government can do when commodity prices fall. But it's certainly a chink and a risk to the public view of Bill English and the party as a whole as sound economic managers.

That's why this isn't the last we've heard of Solid Energy. And that's why Labour will keep asking John Key and Bill English about the hole Solid Energy has dug itself, hundreds of millions of dollars deep. They might even ask National to show them where the money went.