Simon Green is professor of politics and co-director of the Aston Centre for Europe at Aston University in the UK.
London (CNN) -- There will be few set-piece events in David Cameron's political career that will be more eagerly awaited and closely watched than Wednesday's long-promised speech on the UK's future relationship with the European Union.
In it he had to attempt what must have seemed like Mission Impossible. On the one hand, he needed to respond to his own Conservative Party's increasing clamor for a referendum on Britain's membership of the EU. And on the other, he needed to address the major international concern over Britain's apparent detachment from the rest of the EU, reassuring both the UK's partners in Europe but also President Barack Obama in the United States.
To his credit, the PM's message was carefully crafted and deftly handled: he left his audience in no doubt that he personally wanted to keep Britain firmly in the EU. He pointed out that the EU without Britain would be a weak organization. He also pinpointed a number of genuine challenges for the EU -- the eurozone crisis, global competitiveness and the persistent problems of democratic legitimacy.
Laying out these issues may be seen as a pragmatic vision of European integration, which is moreover widely shared by other member states. But inevitably, it is his promise to renegotiate the UK's conditions of membership and put the results to the British people in a referendum, to be held if the Conservatives win the next general election in 2015, for which the speech will be remembered most.
The growing band of eurosceptics within the Conservative Party has demanded a referendum on continued British membership ever since Cameron managed to wriggle out of a commitment to a public vote on the Lisbon Treaty by a technicality. What is more, the UK Independence Party, which campaigns for outright exit, is currently riding high in the polls; many of his MPs and strategists fear that UKIP will split the Conservative vote at the 2015 election, thereby consigning the party back to the opposition benches.
The pledge to hold a referendum after 2015 will therefore be heralded by the eurosceptics as a major strategic and tactical victory. In turn, the PM may hope that this pledge will neutralize their complaints. History would suggest, however, that such appeasement rarely silences rebellious voices, but rather emboldens them.
Furthermore, by playing to what is ultimately a domestic audience, Cameron is stretching the patience of European partner-states ever further. Practically all member-states have accepted, albeit grudgingly, that the UK is now adopting an à la carte approach to integration, for instance by not adopting the euro or participating in the common immigration policy. However, the suggestion that other existing aspects of integration, for instance in social rights, should be re-opened for Britain to opt out from retrospectively is typically met with incredulity in European capitals.
Yet, without agreement by each of the other 26 member-states, this renegotiation will amount to nothing. In recent months and especially in the run-up to the speech, the German government has been on an explicit charm offensive but at some stage in the not-too-distant future, German Chancellor Angela Merkel will presumably conclude that there is no longer any point in engaging with the UK.
All of this leaves Britain in a precarious position. A major attraction for inward investors to the UK is the fact that it is a full member of the EU, as opposed to a partial member like Norway and Switzerland. Crucially, the mere prospect of a referendum in the next five years is likely to affect investment decisions being taken now. The Obama administration has made it crystal clear that it values the UK because of its membership in the EU, not despite it.
Most of all, the promise of a referendum after renegotiation raises the prospect of a self-fulfilling prophecy: for if the renegotiation yields only minor concessions for Britain, as is highly likely, then voting for exit becomes the only logical conclusion.
Of course, it may never come to this: the necessary domestic political prerequisite for a referendum, namely a Conservative parliamentary majority after 2015, is by no means assured and the opposition Labour Party has confirmed its rejection of a membership referendum on any terms. Europe plays no significant role in the priorities of voters whose main concern is the state of the economy. But in attempting to extricate himself from between a rock and a hard place, Cameron has just made one of the biggest political gambles in British political history.
The views expressed in this commentary are solely those of Simon Green.