Key Points:

It was only a few short weeks ago that Bill English was saying he wasn't going to be spooked by a little bit of red ink in the Government's accounts.

The Treasury's pre-election fiscal update bleeds so much of the red stuff that the document looks like the aftermath of Dracula running amok in the blood bank.

The numbers in this horror story are truly awful. It is goodbye to operating surpluses for close to a decade. The forecasts for the separate cash deficit figure nearly double to $6-7 billion for the foreseeable future. Growth slumps. Unemployment jumps. These numbers will almost certainly get worse. The Treasury's forecasts were done before last week's maelstrom on Wall Street.

The update is a brutal reality check for parties making big election promises. In the short term, Labour has already gobbled up the allocation for new spending in next year's Budget. There can be no pre-election bidding wars to buy votes. Post-election negotiations are now going to be hellishly difficult.

In such an atmosphere of restraint, National's unveiling of its tax cuts tomorrow seem about as tactful as someone cracking open the champagne at a funeral just as the coffin is being lowered into the grave.

But Michael Cullen did not lay into National yesterday - and for good reason. The update's forecasts have obliterated previous boundaries of the tax argument.

Having slammed National for setting a debt-to-GDP target of 22 per cent, Cullen's position has been undercut by the current debt ratio being forecast to balloon from 17 per cent to 24 per cent of GDP over the next four years.

If National's tax cuts are reckless, so, by Cullen's previous definitions, are Labour's.

Cullen admitted as much by saying that had he known in advance what was going to happen he would have been more cautious about cutting taxes. However, he is refusing to withdraw the second and third phases of Labour's tax package.

That gives National carte blanche to go with its more generous package, which it says will be no more expensive than Labour's because the extra cost will be funded by transparent savings in government spending.

The bickering over tax has long made up for the lack of argument over wider economic policy. Yesterday changed everything. The election is no longer about tax. It is about which party can best convince the voters its policies will shorten the length and depth of that recession.