The thought that we are probably less than fourteen weeks away from a general election is hardly one to set the pulses racing. Unless the polls prove to be spectacularly wrong, the only imponderable – the ‘known unknown’, as Donald Rumsfeld would put it – appears to be the size of the Conservative defeat.

The only possible salvation for the Conservatives would be if, over the next few weeks, there emerged an ‘unknown unknown’; an explosive issue which could shake the country’s political foundations and upset the predictions. What Michael Howard would give to be able to campaign on a subject on which he and the Conservatives were, alone in British politics, in tune with the public will. How he must dream of a deus ex machina arriving centre stage to present him with a cast-iron popular vehicle. Imagine if he could find a theme on which he had the support of over two thirds of the public.

It has arrived. He has that theme.

This week a wild card was introduced into British politics, with the potential to transform its dynamics and give momentum to the moribund forces of the centre-right. On Wednesday, Jack Straw published the European Union Bill, which enshrines in law the forthcoming referendum on the proposed EU constitution.

The election result may seem cast in stone, but the impact of the referendum campaign could, in the medium term, be transformative on British politics.

In today's Telegraph, Anthony King analyses the first poll based on the government's newly announced referendum question, which shows a two to one 'no' majority. As he puts it: "the Yes camp has a far tougher fight on its hands than it did three decades ago".

The political dividends to the Conservative Party should be immense. The divide between the parties is stark. On one side are Labour and the Liberals. Labour is, in the public mind, the clear villain, having agreed to a constitution which less than a quarter of the country wants. With them are the Liberals, who simply say yes anything with the prefix ‘EU’ attached.

On the other side is the Conservative Party, which now has an issue – indeed, has been handed it on a silver platter by the government - on which it speaks for the majority of the country. As if that was not enough good fortune, Tony Blair – the great hoover of Conservative causes and natural Tory territory - is, on this most fundamental of subjects, merely the voice of a small sect of committed ideologues.

The Conservative Party has been looking since the 1992 election for a thread to bind itself together, and to attach itself to public support. For the first time, it now has just that. The debate over the constitution is no longer (just) a theological dispute. It is a live political issue, and the Conservatives’ stance is supported by a two to one majority of the public, by most entrepreneurial businesses and by most newspapers.

It is almost impossible to imagine a more propitious political outlook for a party needing to re-establish its credentials as the voice of middle Britain.

And yet. Given its recent history, the chances are that the Conservative Party will prove incapable of recognising the gift horse which the government has planted squarely in its mouth. It is a damning commentary on the state of the Conservative Party that few wise gamblers would back the Tories even in a one horse race. The referendum campaign could well be a walk-over for the ‘no’ campaign. But does anyone really imagine that it will provide the springboard for the Conservatives’ revival? The evidence of recent years suggests that, given the opportunity, the party relishes any opportunity to mess up.

If, for once, the party can break free of its introspection, its factionalism and its self-immolation, it has the opportunity once more to speak for Britain. We are listening.