By Andrew Marr BBC News political editor

The Budget is a calculated gamble, but it is also a gamble on the basis of a lot of ignorance.

It is a gamble that the public means what it says when it says it wants more money spent on health - and that it is prepared to pay for that through tax.

For the last five years there has been a kind of cloud hanging over British politics

That is a fairly big risk in this country and in others.

It is a gamble above all that the health service will actually be able to deliver visible improvements by the time of the next election.

The chancellor is gambling that these vast amounts of money will not simply go on staff pay increases and paying off debts - or buying computer equipment and all sorts of things the NHS wants to do.

That will not help Labour convince voters that this has been worth it.

Public anger

But there was another gamble and another risk that was considered to be worse.

For the last five years there has been a kind of cloud hanging over British politics, at least intermittently.

That has been the question of what Labour is for anymore.

It is worse for Labour, they have decided, to appear to stand for nothing

Is it simply there to run the economy efficiently, to be close to the Americans, to be a kind of alternative, small 'c' conservative party? Does it really have a purpose?

The questioning and the anger about that erupted at the time of the last election when voters became increasingly annoyed that this Labour government had completely failed to improve the health service and other services - and indeed they were often getting worse not better.

It is worse for Labour, they have decided, to appear to stand for nothing than to do what they may well have done, which is to take hundreds of thousands of voters, particularly better off voters, and start to push them off towards the Conservatives.