Analysis By Nick Assinder BBC News Online political correspondent

It is already clear which way the debate will go

That is not what the question on the referendum ballot paper will ask, of course.

That will be a far more simple question along the lines of whether the government should accept the new constitution - yes or no.

But from everything Tony Blair and his ministers have said since they executed the extraordinary U turn, it is clear how they plan to run the "yes" campaign.

In his announcement to the Commons on Tuesday, the prime minister lost no time in insisting that those pressing for a "no" vote were really only interested in pulling the country out of the EU.

Secret agenda

The Tories, he suggested, had a not-so-secret agenda to re-negotiate EU treaties which would have the inevitable effect of leading to withdrawal.

It is now absolutely certain that this, probably 18-month-long campaign, will be about Britain's future in the EU rather than the relative merits of the constitution

"It is time to resolve once and for all whether this country wants to be at the centre and heart of European decision making or not, time to decide whether our destiny lies as a leading partner and ally of Europe or on its margins," he told MPs.

The implication was obvious and was further underlined by his official spokesman later that day when he declared: "There are clear implications about our future in Europe and therefore this debate should not be about the myths."

The theme was taken up with even more gusto by Trade Secretary Patricial Hewitt when, speaking on the BBC's Today programme, she lumped the Tories together with the anti-European UK Independence Party.

She was even more direct in her assertion that the Tories wanted to pull out of the EU.

Myths

That, however, is not Michael Howard's stated position.

He has insisted he wants the UK to remain in a reformed and modernised EU where those pressing for a United States of Europe have been defeated.

To suggest anything else is a deliberate misrepresentation of the opposition's policy, he claims.

Labour, on the other hand, insist the Tories are misrepresenting the government's position by pedalling myths about the creation of a European superstate.

Either way, it is now absolutely certain that this, probably 18-month-long campaign will be about Britain's future in the EU rather than the relative merits of the constitution.

Polling evidence

And there is a very good reason why the prime minister will be happy to see that as the core of the campaign, other than the fact that he may well believe it to be the real issue.

All voters appear to want more than anything else is information - clear, unbiased and unspun facts about what the constitution does

All the polling evidence suggests that, at the moment, voters would probably reject the constitution and are certainly opposed to a European superstate.

But it is also the case that most probably believe the UK's future lies within the EU.

In other words, it would be easier for the government to win a vote on remaining within the EU than a poll on the constitution itself.

Obviously, part of the prime minister's job during the campaign will be to try and portray the constitution as a positive development for the UK which poses no threat to the nation's sovereignty.

'Tidying up' exercise

But winning voters around to that view will be a far more difficult task than simply asking them whether they want to stay within the EU or pull out.

As for Mr Howard, his task will be to persuade voters they can reject the constitution without undermining the UK's position in Europe.

Indeed, he will argue it would lead to a far more flexible and less threatening Union, more to the taste of British voters.

Meanwhile, what all voters appear to want more than anything else is information - clear, unbiased and unspun facts about what the constitution does.

Is it a tidying up exercise or is it a fundamental shift in the nature of the EU?

Whether they feel they can trust the rival political camps to give them that information is another matter.