Referendums are a thoroughly unsatisfactory form of democracy. They frequently fail to answer the question on the ballot paper, ending up as a vote of confidence in the government of the day. And they have a built-in tendency towards preservation of the status quo.

All too often such exercises are used by governments to disguise their own internal divisions. They can also be a populist trick to undermine parliaments - as Germany learnt to its cost in the 1930s. If the issue at stake is not a question of burning public interest, it is very difficult to motivate voters to vote at all.

All things considered, therefore, the 42 per cent turnout in the Spanish referendum on the European Union's constitutional treaty last Sunday was rather creditable, particularly since the outcome - an overwhelming Yes - was widely predicted.

It is not going to be anything like that easy to win approval in several of the other nine referendums to come in the EU - particularly in France, the Czech Republic and the UK. The turnout will matter. So what will motivate voters to go to the polls?

This week's visit by President George W. Bush to Brussels provided one answer. He came to talk to Europe. He divided his time between the Nato alliance and the EU, carefully blurring any hint of favouritism for either institution. It was a visit of fine words without much substance, a delicate balancing act to avoid reopening old wounds.

Behind the diplomacy, however, the reality is increasingly clear: the big issues of transatlantic relations will in future be conducted between the US and the EU and not in Nato. As Gerhard Schröder, the German chancellor, undiplomatically spelt out just one week earlier, Nato has ceased to be the forum for discussing strategic issues.

Yet if the EU is going to be the main interlocutor for the US in Europe, it has to try harder to build a common foreign policy. That is something the constitutional treaty is supposed to help with. It creates new jobs of a full-time president of the European Council, an EU foreign minister and a beefed-up European diplomatic service. It is one of the few areas where the treaty actually breaks new ground, rather than simply consolidating existing arrangements.

So will it make a difference? Yes, but as so often with the affairs of the EU, only with time and political will. Will it mean that the EU suddenly speaks with one voice when an American president drops by? No, but it may at least sound a little more coherent.

Like any EU treaty, this one is inevitably a compromise. It seeks to reconcile the national interests of the member states, while helping them come to joint decisions in the EU institutions. So the plans for strengthening foreign policymaking are a fudge that will create new spokesmen and give them new resources, without abolishing national foreign ministers and embassies. It leaves EU governments in effective control and limits the powers of the European Commission.

That is why the new foreign minister is going to be "double-hatted", with a seat both in the Council of Ministers and the Commission. He or she will chair the monthly meetings of the 25 foreign ministers and also sit in the Commission as a vice-president. The minister will be a servant of the member states, while also bound by the "college" of commissioners.

It is certainly not going to be an easy task, as a thoughtful analysis* by Brian Crowe, the British diplomat who served in Brussels for eight years as director-general of external relations for the Council, points out. He or she will have loyalties to at least three different constituencies, including the future council president, who will also represent the EU internationally. But at least by combining the tasks the future minister should help minimise conflicts - not least with the Council presidency.

It will be a balancing act, too, between the big member states and the small - on occasion allowing Britain, Germany and France to take the lead (as they have done in negotiating with Iran) but always seeking to ensure the views of the rest are reflected. Javier Solana, the present "high representative" for foreign affairs, has steadily increased his authority and powers of initiative in areas such as the Balkans and the Middle East peace process. On Ukraine, he threw his weight behind the presidents of Poland and Lithuania, when the Big Three held back. Yet where Britain and France have been hopelessly divided, as on Iraq, he has been powerless.

What Mr Solana lacks is a budget and many staff. Both would come from the Commission under the new constitution. Sir Brian concludes that in spite of the "tangled web" of powers, the new job amounts to a big step forward for a common foreign and security policy (CFSP). Yet its real success or failure will be decided by the most difficult single issue - relations with the US.

"There will always be a hole at the heart of the CFSP until we Europeans have a common approach on how best to influence the policies of a US that bestrides the world stage," Sir Brian says. The constitution alone cannot resolve that. Tony Blair and Jacques Chirac hold the key.

Still, at least the constitution gives voters a relatively clear choice: if they want to open the way for more common foreign policy, vote Yes. If they want less, vote No. Is that clear enough?

* Foreign Minister of Europe, by Sir Brian Crowe, published by the Foreign Policy Centre

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