It is not just Britain which would be damaged if it quit the European Union. So would other members. Jean-Claude Juncker’s nomination as Commission president at last Friday’s summit increases the chance of Brexit – Britain’s exit from the EU. Leaders from all countries now need to work to limit the risk it happens. David Cameron went out on a limb to block Juncker, and failed. The UK prime minister mishandled the diplomacy, notably by seemingly threatening to pull out of the EU if the former Luxembourg premier got the job.