Leading article: Mr Darling announces the election ahead of time

His politically astute Budget throws down the gauntlet to the Opposition

The Chancellor presented his Budget in characteristically sombre and low-key style, but the imminence of the election positively screamed from every sentence. And in electoral terms, he offered MPs an artfully produced package. His combination of steadiness, caution and championing of the poor left a sound impression and – depending, as always, on the small print – may end up doing Labour's election campaign some good. If, less ambitiously, the over-riding objective was to do no harm to Labour's election chances, Alistair Darling's Budget must be accounted a success.

He played a weak hand well, making the most of the good news and diverting the bad. He boasted gently of tax receipts that were better than expected and borrowing running (a little) below forecasts, insisting that, in coping with the – "global" – financial crisis, "the right calls were made". To drive the point home, he listed the indicators that might have turned out worse – if, as he left his audience to imagine, others more panicky and less experienced had been in charge: registered unemployment, repossessions, family hardship could all have been higher.

He noted what he saw as the fragility of the recovery – it was, he said, still "in its infancy" – which meant it needed to be nurtured, and growth should not be jeopardised by premature efforts to slash the deficit. And he continued his tradition of inspired borrowing from others, filching the suspension of stamp duty on sub-£250,000 houses for first-time buyers from the Conservatives, while announcing that he would pay for it by raising the stamp duty rate on £1m-plus properties – a neat piece of old Labour arithmetic, which also owed something to the Liberal Democrats' planned "mansion tax".

He raised laughter with his dig at the Conservatives over Lord Ashcroft's tax status, listing new tax disclosure agreements with, among others, Belize. He announced a rise in child tax credit for one and two-year-olds, spelling out that the rise would apply regardless of the marital status of the parents. And he claimed that tax credits generally – which the Conservatives and Liberal Democrats would abolish for the better-off – had helped those forced into short-time or lower-paid jobs by the recession.

In all, this was a shrewdly political performance, clarifying some of the dividing lines with the Conservatives, and playing at once to several constituencies, including the anxious middle classes. One conspicuous measure of Mr Darling's success was the difficulty that the Conservative leader had in mounting an effective response. Rarely more impressive than when required to think on his feet, Mr Cameron scored fewer points than usual and was reduced too often to generalised invective.

Which is not to say that this Budget should be accepted at face value or that there is no further argument to be had. There is a budget for an election and a budget for the nation's future, and the two are not necessarily the same thing. What Mr Darling did yesterday was to fire the opening salvoes of the election campaign and secure some of the territory from which Labour intends to fight. But he was singularly vague about where the spending axe might eventually have to fall, and his attention to small business overshadowed the expectation of lower public spending that could reduce opportunities for those very same businesses.

There is also room for scepticism, if not outright cynicism, about some of projections for growth and borrowing until 2015, not least because of the likelihood of a change of government and the virtual certainty of a change of Chancellor. It is fine for Labour to favour growth over deficit-cutting in order to protect a weak recovery, but a government can afford to be profligate if it does not expect to pick up the tab.

Nor is Mr Darling's diagnosis of the crisis as it affected Britain beyond dispute. Did government policies, including dependence on financial services, so-called soft-touch regulation, and a high tolerance for debt, render this country particularly vulnerable? The Conservatives' free-market approach has made it hard for them to capitalise on Labour's discomfort in this respect, which is where there is an opening for the Liberal Democrats, with their continuing calls for tougher financial regulation and their own well-defined spending cuts.

It is the merits of these competing arguments that the coming election campaign should largely be about. The Chancellor has said his piece. This is one of those rare times when the deciding vote will come not from Parliament, but from the people.