Perhaps the French might elect a Front National president who would withdraw France from the EU. Perhaps other countries might follow the UK’s lead in having their own In-Out referendum and for many of them the choice be Out. Perhaps some country such as Greece or Italy might be driven out of the euro by financial or budgetary problems, with this triggering a financial crisis that induces a more widespread collapse. Perhaps the attempt to push deeper political integration might fail, with some required new Treaty being rejected, at ratification stage, by many member states, leading to a widespread crisis.