Leading article: First round to the Tories, but the debate remains unreal

Cameron has won on National Insurance but failed to answer his critics

It is good that at this stage of the campaign minds are having to concentrate on the solid question of tax. The Tories have scored an early goal here. After weeks on the backfoot, David Cameron has seized the initiative on Labour's proposed increase to National Insurance and found an issue he can run with.

Doubtless to his own surprise – the whole business had the air of a rabbit being desperately plucked from a hat – the Tory leader finds wind in his sales. The Prime Minister's suggestion that Tories bamboozled business leaders over National Insurance has also backfired, with some of those leaders pointedly asking not to be treated like fools.

The Tories are right to capitalise on Gordon Brown's discomfort on tax. Labour under Tony Blair cosied up to business, neutralising a once powerful foe. Conservative strategy must be to chisel away at this alliance in the hope of revealing a gulf between Labour and the business community. Voters can only benefit from any debate that ensues. It would animate the campaign more, of course, were the Tories forced to reveal further details of their plans for tax and the public deficit.

The Liberal Democrats have sounded more convinving here than Mr Cameron's team. But neither opposition party, nor the Labour Party, has unveiled anything like a fully comprehensive plan to lower public expenditure, even though almost everyone now accepts that it must come down hard. All prefer to stick to the same safe talk about "savings" to be found in the public sector that will shave off a billion here and a billion there, none of them mentioning that even if these theoretical savings were found – which is unlikely – they would make precious little difference to the overall debt.

This collective display of party political cowardice over the tens of billions – not billions – that need to be cut, is depressing but not surprising. In the first genuinely close election in decades, no party wants to frighten off a single voter. Distrust of the electorate, and of their maturity, is rampant among party strategists, hence the parties' reliance on safe slogans.

The two main parties are also trapped by their recent rash pledges. Labour is hamstrung by Mr Brown's initial bid to position the election as a choice between "Labour investment" and "Tory cuts". When that unconvincing claim failed to impress many people the party calibrated its message, so that Labour now appears to promise both cuts and investment at the same time. The Tories are just as fork-tongued. While Mr Cameron dwells on the summery theme of hope, his would-be chancellor, George Osborne, prefers the wintry theme of austerity, begging the question: which is it to be?

There is another reason why both main parties are so decidedly coy about their spending plans. Having ring-fenced health and education, the two biggest consumers of public money, the next government does not actually have much room to cut elsewhere, unless it plans to close down entire ministries. It can hardly make savage inroads into defence either, while troops are still in Iraq and Afghanistan.

Running scared of the voters as they are, the two big parties have even ruled out a rise in VAT. Another topic slapped down before anyone even debated it. Many must be wondering if voters will ever have the chance to join a serious discussion on tax and spending before 6 May. The sight of all the parties having to engage on National Insurance was refreshing, but it was only a start.