Steve Richards: Cameron is giving us more questions than answers

ITV hopes that more than 10 million viewers will tune in to tonight's televised debate with the party leaders. I hope the intensively rehearsed drama lives up to expectations. One of the joys and torments of politics is its glorious unpredictability and no one knows for sure what will happen when the cameras roll.

Nonetheless, I sense that the most significant event of the campaign has already taken place. I also have a hunch the most important straw in the wind has blown by already, an indicator at the height of the battle as to what might or should happen when hostilities formally cease.

First to the event that historians will conclude was more decisive than any other. The launch of the Conservative manifesto earlier this week and the document itself was extraordinary, one that breaks the mould of such events in ways the media has understated. In its counter-intuitive, thought provoking and stand-out distinctiveness the launch reminded me of Labour's equally extraordinary shadow Budget, presented during the 1992 election campaign, another moment that came to be seen as pivotal.

I am not arguing that the Conservatives' equivalent this week will necessarily have the same calamitous impact on them as the shadow Budget had for Labour in 1992, but I suspect when the post-election reviews are held it will be seen one way or the other as the key moment. Strategists from all the parties will look back and conclude either that this was when David Cameron sealed the deal or when he blew it.

After Labour's shadow Budget, no one knew for sure how voters would respond. Many commentators thought it a brilliant stroke at the time. Conservative Central Office watched it nervously. Only later was it blamed for Labour's defeat. If Labour had won it would have been singled out as the event that swung it for them.

The Conservatives' attempt to swing it for them is an echo of Thatcherism and not a break from it. In John Campbell's outstanding biography of Margaret Thatcher there is a section on her period as leader of the Opposition that is oddly familiar. He highlights a speech on social policy in March 1978, when Thatcher hailed voluntary effort and declared: "Once you give people the idea that this can be done by the state then you deprive human beings of an essential human ingredient – moral responsibility." Campbell writes that during her opposition years, in a series of speeches, she paid glowing tribute to Dr Barnardo's, the NSPCC and the RNLI, pointing out that none of them were reliant on the state. Like Cameron she called it "social responsibility".

So partly the Conservatives' approach is re-heated Thatcherism. But what a re-heating. The Conservatives' entire manifesto was predicated on the single idea of redistributing power to the people in order to form the big society. The manifesto was closer to an argument than a programme. At the launch, only Michael Gove gave a passing nod to the demands of orthodox politics, when he said that the state would often provide the cash to help people to help themselves. In doing so he raised a thousand questions.

Who decides how much money? How will it be raised? How will the cash be accounted for? Suddenly the state is pretty active in the big society. I am still not sure how it would work and where the lines of accountability would fall. But what I do know is this is the vision that Cameron and those closest to him have been working on for years and what some of them are in politics to bring about. The mind-boggling emphasis means they have no choice but to try to succeed if they win. There was no mention of Europe and immigration at the launch – although bleak, parochial policies are in place – and the economy hardly got a look-in either. This week they conveyed an argument. The means are vague but the clarity of the broader vision sets them a test. If the poor get poorer and schools, hospitals and trains get worse, they will have failed, whatever happens to the deficit.

The argument and its projection will either propel them to power or reinforce their lack of readiness for government. I have no idea which, but I am sure it will determine the outcome of this election or be seen to have done so.

In this strange campaign, the launch of the Liberal Democrats' manifesto felt much more like the unveiling of a programme of a conventional alternative government, which was of course partly the calculated intention. Vince Cable was there to remind us of the deficit and in his opening gambit read out a long series of proposed cuts, some of them vague, all of them familiar. The contrast to the slightly happy clappy mood of the day before was marked. Nick Clegg described it as "optimism in touch with reality", a clever phrase and what Tony Blair might call a tonal third way.

Beneath the deliberately subdued seriousness the Liberal Democrats are proposing the most openly redistributive tax changes of any party. Clegg even dares to use the term 'redistribution', a word that Gordon Brown rarely utters. Labour's is the most redistributive of any of its manifestos since 1992, the election in which it launched its fatal alternative Budget, but on taxation the Liberal Democrats are more daring than Brownite New Labour are now.

There is no point probing Clegg's plans in the event of a hung parliament. As he has said the voters will largely decide what he would do next. But yet again yesterday he refused to say how he would respond if the Conservatives secured more votes and Labour more seats, an intriguing evasion. Perhaps under those circumstances he plans to declare that the system is rotten and call for an immediate referendum on electoral reform, one that Labour has committed itself to, although not for more than a year after the election.

Currently leaders are posturing in the midst of a campaign. This is not 1997, when Labour and the Liberal Democrats are more or less united against a discredited Conservative government. But once the battle has ceased it is difficult to see how Clegg's commitment to sweeping changes in taxation, support for electoral reform and Europe makes any formal arrangement possible with the Conservatives.

Evidently the Transport Secretary, Lord Adonis, a former Liberal Democrat, has reached the same conclusion. In this newspaper he called in effect for Labour and the Liberal Democrats to revive the spirit of 1997 and keep out the Conservatives. Like the Conservatives' launch, Adonis' authorised intervention was also more extraordinary than most of the media suggested. It is a tradition in elections for the bigger parties to affect confidence that they are heading for victory. Labour gave up doing that long ago, admitting they are underdogs. Now Adonis makes the semi-defeatism more vivid by implicitly accepting that a hung parliament is the best that Labour can hope for.

It is the best that the Liberal Democrats can hope for too. Speaking to one of their most insightful MPs recently, he argued that this election is make or break for his party. If there is no breakthrough this time, after the simultaneous political and economic crises, he could not envisage another decade of sitting on the margins at a national level wondering when a hung parliament might turn up.

Will it turn up this time? The answer hinges on the voters' verdict on the mood music around Cameron's launch earlier this week, and what they conclude it tells us about him and his party.

s.richards@independent.co.uk