Cameron's UK win has implications for Europe beyond a possible Brexit

Now Europe's shock at David Cameron's surprise electoral victory has worn off, there is a growing realisation that he is already reshaping the debate about Europe's future. The Conservative Party has pledged to hold a referendum by the end of 2017 on whether Britain should leave the EU. Cameron wants Britain to remain, but a Brexit remains a possibility.

EU member states will have to decide if new initiatives will help or hinder Cameron's campaign to keep Britain in the EU, says Vivien Pertusot, of the French Institute of International Relations, a Brussels thinktank. "The UK debate about EU membership is no longer just a British debate, but a European one. Cameron will come to the table with demands that can affect the development and functioning of the EU as a group of nations. Some policies may now be delayed. Others may never see the light of day."

The threat of a Brexit is already casting a long shadow. "All capitals in Europe will have to think hard about this, again and again. Cameron will say, 'you have to give me something that I can sell back home'," says Pertusot. The Conservative victory will likely impede the drive for further federalisation. "There will be a temptation to slow down negotiations and wait until 2017, so as not to give ammunition to the anti-EU group in Britain."

The potential departure of Greece from the Eurozone will also help Cameron's agenda. Two high-profile exits would trigger seismic reactions from which the EU would find it difficult to recover. For now, Brussels wants to placate rather than confront Britain. Jean-Claude Juncker, the president of the European Commission, the executive arm of the EU, says he wants a "fair deal with Britain" and that the Commission will examine in "a very polite, friendly and objective way" the UK's "proposals, ideas or requests".

Donald Tusk, the president of the European Council, which sets the EU's political agenda, called on the new Conservative government to make the case for Britain to stay in the EU, while indicating support for some reforms. "A better EU is in the interest not only of Britain but every member state," Tusk says.

Red lines remain, say EU diplomats. Treaty change is off the agenda, as are restrictions on the free movement of labour. In France, President Hollande congratulated the British prime minister and invited him to Paris. But there is scepticism over whether Cameron can perform a balancing act between the pro- and anti-Europeans in his party. "Cameron has won a clear victory, but whether he can enjoy it is another matter," says a senior French official.

German politicians reacted cautiously. Germany understands that Britain's debate about EU membership is part of a wider discussion about who Britain is and what it wants, especially after the Scottish independence referendum, says Moritz Schuller, political opinion editor at Tagesspiegel, a Berlin newspaper. "[The EU referendum] is not just a Tory attack on Europe, a whim of David Cameron. And a Tory government is better for Angela Merkel than a Labour one, because that would have started a debate about austerity and a Europe-wide move to the Left, something she would like to avoid."

Europe's leaders know how weak they are, says Schuller, and will be open to debate. "Cameron should not come up with particular demands but insist on a high-level commission that collects everyone's grievances. Divide and rule: given the euro debacle, there are more pro-reform minded people than ever before."

For that, however, Cameron will need allies. Hungary's prime minister Viktor Orban, the only European leader to vote with Cameron against the appointment of Jean-Claude Juncker in 2014, welcomed Cameron's triumph, praising him handsomely. "There are two types of politics in Europe today: the politics of the courageous and the politics of the fudgers. Mr Cameron is beyond doubt in the courageous camp: his politics are forthright and brave and he is willing to engage in debate."

Some central European countries have been alienated by the Tory party's anti-immigrant rhetoric, but Orban is even more strident about the need for Europe to close the door. The Hungarian prime minister can now use Cameron's re-election to legitimise his own euro-scepticism and hard line on immigration, says Peter Kreko, of Political Capital, a Budapest thinktank, but this is risky. "The same arguments that Orban uses against immigrants here are also used in the UK against Eastern Europeans who settle there."