Dominic Lawson: It's not enough for Cameron to be the anybody-but-Gordon candidate

As the Daily Mirror is Labour's eternal mouthpiece – it performs the same function for the Party as L'Osservatore Romano does for the Vatican – we can be fairly certain that it is well-briefed on the Government's election planning. So I am inclined to believe its "exclusive" report that today Mr Tony Blair will make a "dramatic re-emergence on to the political stage" with a speech at a Labour rally in his old constituency HQ of Trimdon.

As the Mirror puts it in its inimitably partisan reporting style: "He will point out the ugly truth beneath the touched-up photos and PR spin that the Tories are still the hard-right party with extremist policies that they were under Margaret Thatcher.... His return has been timed to deliver a hammer blow to Mr Cameron's sinking campaign."

Those of a more detached disposition might think it is in fact only because Gordon Brown is so desperately unpopular among the sort of South-eastern voters whom Blair pulled into New Labour's orbit, that the former Prime Minister has been prevailed upon to address this pre-election rally. They might also wonder why even those still attached to the legacy of Tony Blair should vote for Labour because of whatever he might say at such a rally: it's not he who is proposing to be re-elected as a Prime Minister, or even to be a Member of Parliament.

Still, if such a coup de theatre is as potent an electoral anti-Tory missile as Labour obviously thinks it is, I have a suggestion for a Conservative anti-anti missile. They could ask John Major to play a similar role in their own campaign. What, the John Major who presided over the humiliating fiasco of Britain's exit from the European Exchange Rate Mechanism? The John Major who, in 1997, led the Tories to their worst electoral defeat since 1906 (or 1857, depending on which psephologist you listen to)? Yes, that's the man.

Yet if the Conservatives want to remind the electorate – and they surely do – that the national accounts were handed over in fine fettle to New Labour, which then systematically debauched them, who better to put into the nation's television studios during the campaign? John Major is one of those political figures whose reputation has greatly benefited from a period of absence from the public scene, although he was never, even in the depths of the Conservative's plight in 1997, personally unpopular. His memoirs sold astonishingly well, and his publishers told me with unaffected amazement how successful his various book tours were (this at a time when the Conservative Party was still an official laughing-stock).

Yet, as the Mirror's story illustrates, it is not the person who was Tory Prime Minister between 1990 and 1997 that Labour want us to be reminded of during the forthcoming election campaign, but the one who was PM for the 11 years before that: Margaret Thatcher. To which many, if not most, Conservatives would say: we wish. There is no mistaking the suppressed irritation, even anger, among Conservative associations across the country at the failure of David Cameron to express the party's principles with the clarity employed by their most successful leader of modern times. In particular, they contrast the apparent fuzziness of his message with the certainties and uncompromising campaigning they recall from the party's successful campaign in 1979 – the last time they won an election against a Labour party in Government.

They are both right and wrong in drawing such a contrast. They are right in that the 1979 manifesto was a bracingly clear statement of Margaret Thatcher's principles, written with a genuine sense of fury at Britain's demoralisation and habituation to national failure. On the other hand, as one of her closest aides reminded me last week, "there were very few firm commitments in that manifesto: it was a very light document in terms of concrete policies". This was not disguised even at the time. In one of the opening paragraphs, Thatcher admits: "Those who look in these pages for ... detailed commitments on every subject will look in vain." There were a few hard nuggets: there was a pledge to reduce income tax, although not necessarily the overall burden of taxation; there was a commitment to cut back the powers of the trade unions; above all, perhaps, as an election sweetener, there was the promise to sell council houses to their tenants. The Conservative Party of 2010 desperately needs a similar policy to that one – something which both appeals directly to the less affluent voters and also sets its offer apart from the Labour Party's promise of nothing but more of the same.

Yet Cameron's internal critics are also wrong: Margaret Thatcher was intensely nervous of alienating the public sector back in 1979. Thus it was that she pledged – against, incidentally, the wishes of her shadow Chancellor Geoffrey Howe – to honour whatever the public sector pay commission of the day would decide was the workers' due. It was a gigantic blank cheque for the public sector: and when, after the election had been won, the Clegg commission duly recommended pay increases averaging 25 per cent, the Thatcher Government had to put up VAT – to general fury – in order to meet the bill.

Similarly, although Cameron's pledge not to cut the NHS budget strikes many Conservatives – and not only Conservatives – as unsustainable and even irresponsible at a time of ruinous Budget deficits, it's worth going back to that 1979 manifesto, to see what Margaret Thatcher said in similar circumstances: "It is not our intention to reduce spending on the health service. We intend to make better uses of what resources are available. So we will simplify and decentralise the service and cut back bureaucracy." Can you tell the difference between that and the Cameron message? Thatcher, like the current Tory leader, was politically terrified of being seen as an enemy of the NHS, which, as one of her chancellors ruefully observed, "is the closest thing the English have to a religion".

It is, however, true that in David Cameron, this fear of saying anything – anything at all – which could be used against the Conservatives by their political opponents, has become akin to pathological. "What terrible accusations will Labour bring forth if we suggest this, or that?" seems to be almost a reflexive cringe governing the Tories' entire electoral strategy. It is indicative of a general lack of ideological confidence, although this is not exactly surprising in the wake of three successive heavy general election defeats, and the undoubted skills of New Labour at black propaganda – or lying, to use the technical term.

I think I can discern how this intellectual wooliness fits into the Tories' overall strategy. They believe that their core vote is rock solid, but that in order to win an overall majority in the Commons, they above all must reassure the sort of swing voters in marginal seats who would in recent elections have voted Labour or Liberal Democrat. So the policies must be wishy-washy enough to appeal to, well, wishy-washy voters. That has a certain internal logic. Yet was it wishy-washiness that turned millions of voters from Labour to Tory, when Thatcher fought Jim Callaghan in 1979?

Her first election manifesto might have been evasive in some respects, but no one could be in any doubt about what the Lady stood for and what she wanted to do. It is insufficient for David Cameron to stand as the "not-Gordon Brown candidate". To win a decisive mandate, and to deserve to do so, it is necessary to win the big arguments.

d.lawson@independent.co.uk