How much, how long for, and will it work? These will be the questions everyone will be scrambling to answer when Alistair Darling gets to the dispatch box.
How much, how long for, and will it work? These will be the questions everyone will be scrambling to answer when Alistair Darling gets to the dispatch box this afternoon to deliver what is being billed as the most important parliamentary announcement since Labour came to office 11 years ago.
No doubt about it. Mr Darling's pre-Budget report, a Budget in all but name, is crucial both for economic stability and for Labour's chances of an electoral recovery. The package could total more than £20bn in tax cuts and public spending commitments.
Mr Darling's prescription, based on the old-fashioned Keynesian idea that the public sector must keep the economy running in a recession, is that the money has to be spent now, and spent big, to stop the global economy sliding into a long slump from which it will take years to recover at an unquantifiable economic and political cost.
Other governments are preparing to follow suit. Barack Obama outlined plans to create 2.5 million jobs in America over the next two years, mindful that he will have to hit the ground running in January to stop the huge US economy sliding off a cliff.
Mr Darling hopes that the package he reveals today will get the economy going again, have people spending up to Christmas and stave off the worst effects of what he hopes will be a short, sharp, shock recession next year.
The Conservatives - outside the international consensus - are warning that the estimated £100bn of borrowing that the Chancellor will have to make to fund the tax-cutting package makes it a high-risk strategy that will saddle taxpayers with having to repay borrowing up to 6% of GNP for years to come.
Mr Darling will attempt to defuse the "tax bombshell" accusation by outlining precisely how he intends for the nation to repay the vast sums of borrowing he will announce.
If the markets do not take fright at the scale of borrowing and the public respond positively to the "fiscal stimulus" then Mr Darling might not just save the economy, he could create an opening for Labour to overtake the Conservatives and make a dash for a 2009 election.
All the hints and briefings and calculations give us a fairly good idea of what the chancellor intends to do with the PBR. He wants to get money circulating in the economy quickly and all the indications are that low earners are the ones who will go out and spend any extra tax bonus immediately.
Expect the government to continue with £2.75bn of tax relief to low earners hit by the disastrous abandonment of the 10p tax regime. The quick fix to the huge rebellion that would have left thousands of low earners worse off is likely to be extended for another year.
A tax cut that will benefit everyone's pocket is the strongly trailed reduction in value added tax from 17.5%, possibly to 15% for at least one year. Given that VAT is a regressive tax - hitting poor consumers harder than rich ones - this is a move that will be popular on the Chancellor's own back benches and it already has the endorsement of former Conservative Chancellor Ken Clarke.
The move could boost spending in shops up to Christmas, but Mr Darling is likely to say that it is only a temporary cut for one year. In itself this would cost the government £12.5bn.
Pensioners could be in for a two-fold benefit. An annual increase in the basic pension based on the retail price index will be boosted by the recent high inflation figures, and there could be an increase in the winter fuel payment, currently £250 a year for the under-80s and £400 for those over 80.
On housing, the government is desperate to get banks lending again and kick the stagnant housing market into action. An extension of the stamp duty holiday on homes costing less that £175,000 is a possibility, but more urgent action is needed on repossessions.
Figures released on Friday showed a record 11,300 homes were taken back by lenders in the past quarter and the government has already announced new rules that force banks to explore every other possibility before issuing a repossession order.
The Chancellor is expected to toughen up the rules further with a three-month grace period for homeowners struggling with mortgage repayments and the extension to the wage ceiling of a government-backed mortgage rescue scheme to keep people in their homes.
Measures to help people in arrears remain in their homes through joint ownership or rent-back deals are being enacted by the SNP government in Scotland.
There are likely to be some populist gestures - increases in vehicle excise duty on older, more-polluting vehicles and the proposed 2p rise in fuel duty might be postponed.
To stimulate the jobs market, public-sector projects from school-building to the Olympics infrastructure and the banks will be told publicly that they have to do more to help small businesses.
Mr Darling is likely to show that public borrowing will balloon from £90bn to £120bn over the next four years, 6% of the GDP. To calm jitters about how we will pay off all this, the Chancellor will also announce that he will cut public spending in future years, squeezing £5bn out of the public sector, and show how taxes will have to rise at the same time.
It is a huge gamble by two cautious politicians, Brown and Darling, and no-one really knows if it will work. There is no objective evidence that the fiscal stimulus will shorten the recession, and despite their astute handling of the situation the political polls leave the big two parties at stalemate.
An ICM survey for a Sunday newspaper found the Conservatives still 11 points ahead of Labour, suggesting talk of a 2009 General Election may be premature. It put the Conservatives on 42% (down one since last month), Labour on 31% (up one) and the Liberal Democrats on 19% (up one).
The main announcements
- A temporary cut in VAT by 2.5% to 15% - the lowest level allowed under EU law - in an effort to boost spending.
- The extension for another year of the £120 rebate for low-paid workers who lost out through the abolition of the 10p tax rate
- An increase in the period of grace before lenders repossess homes, to three months
- The scrapping of planned rises in vehicle excise duty for another year
- A £1bn injection into the small firms loans guarantee, which will enable small companies to borrow up to £1m for over 10 years
