2015 will probably be seen as the year when the terms 'EU' and 'crisis' became inextricably linked. Yet 2016 may prove more challenging still. Chronic instability persists on Europe's frontiers and both the turmoil in the eurozone and the chaos engendered by the arrival of waves of migrants and refugees look set to recur. Moreover, for the first time in its history, the Union faces the prospect of a member state voting to quit its ranks.
The victory of Britain's Conservative party in the May 2016 General Election means the country will hold a referendum on its EU membership by the end of 2017. A British exit could seriously weaken the EU, strengthening Eurosceptic forces elsewhere and potentially encouraging others to attempt the kind of blackmail that David Cameron is currently pioneering. Many factors will determine the outcome of the British poll, including the ability of the Union to effectively deal with the crises confronting it.
Certainly, some of the key determinants are purely domestic. The effectiveness of the Leave and Remain camps will be pivotal in determining the outcome. Of particular importance is the identity of the leader who eventually emerges to lead the latter. Experimental research has suggested that the leaders of the respective camps can have a decisive impact on voting intentions. Whilst David Cameron will lead the Remainers, no strong leader has as yet emerged as his opponent.
Other aspects of the campaign, however, will hinge on factors outside the United Kingdom. First, the timing of the vote itself will hinge on whether, and when, David Cameron achieves his much vaunted renegotiation of the terms of British membership of the EU. This, of course, will depend on other heads of state and government having both the desire and the necessary bandwidth to focus on finding a solution to the British problem. Cameron's plans for the December 2015 summit were ripped to shreds by the Paris terrorist attacks and their aftermath. Events can scupper the best laid plans.
When it comes to the referendum itself, the British public's perceptions will be crucially shaped by events elsewhere in Europe. Central to the campaign is the issue of risk. Both sides are attempting to portray their own preferred outcome as safer than the alternative.
The Remain camp, has emphasised the uncertainties and potential costs associated with British exit - they are already being labelled 'Project Fear' by their opponents. For the Leavers, in contrast, the objective is to make continued membership appear as the riskier alternative. And it is here that the ongoing crises afflicting the EU - and the prospects for these in 2016 - feed into the narrative, in at least two crucial respects.
First, recent research has revealed a close correlation between attitudes to Brexit and attitudes towards immigration, particularly since the 2003 enlargement of the EU. The same research has also pointed out that the public has been sensitive to changes in migration from the rest of the EU in terms of its impact on perceptions of EU membership.
On the one hand, this points to the importance of Mr Cameron securing some sort of deal that appears to address the issue of intra-EU migration. Frankly, it is hard to see what he can achieve on this score via his renegotiation. Britain has already opted out of the EU's visa free travel area - Schengen - and the quota system for distributing those refugees who have arrived in Europe. Given that EU law prohibits discrimination against workers from another member state on the grounds of nationality, his options are highly limited.
The Leave campaign, moreover, have proven relatively successful to date in muddying the waters of the migration debate. In particular, they have set about conflating the issue of intra-EU migration with fears about the refugee crisis currently assailing the Union. Early indications are that scenes such as those witnessed on Greek beaches last summer may reinforce the arguments of those claiming membership carries severe risks
Problematically for the Remainers, the migrant crisis promises, if anything, to become more severe in the year to come. Buried on page 48 of the European Commission's November economic report was an estimate (hedged, it must be said, with numerous caveats) that a further 3 million migrants would arrive during 2016 (some 850,000 arrived in the EU via the Mediterranean in 2015).
Add to this a renewed fear of the threat posed to Europe by terrorism, and the potential for the Leave camp to exploit fears of immigrants and refugees becomes clear. 2015 witnessed three serious terrorist attacks in Europe - in January and November in Paris, and in February in Copenhagen - whilst the rapid intervention of bystanders was all that prevented another atrocity on a high speed train in August. Again, research suggests that there is a potential link between terrorism and electoral outcomes.
Second, there is the state of the eurozone economy. Leavers have long made play of the dangers of Britain being 'shackled to the corpse' of the eurozone. The Commission forecasts growth for the eurozone in 2016. Yet all is not necessarily rosy. Economists predict a recession in Greece in 2016 - the European Commission is expecting a contraction of 1.3%. And major elements of the reforms agreed as part of the 2015 bailout (notably a doubling of income tax on famers and massive changes to the pensions system) are still to be implemented, raising the prospect of still more problems connected to the agreement. Brexiteers will jump on any evidence of the British economy outperforming the eurozone as further evidence of the merits of exit. And another row over a Greek bailout would be grist to the mill.
The prime minister has initiated a process over which he does not enjoy full control. Events within the EU, and indeed outside its borders, will play a significant part in shaping public perceptions of the costs and benefits of membership. Pro-Brexit campaigners will latch on to any evidence of further crisis afflicting the Union and portray them as proof that membership increases the risks to the UK. Should they be successful, of course, 2015 will no longer be seen as the EU's crisis year.
Professor Anand Menon is director of The UK in a Changing Europe where this piece will also appear.