British Prime Minister David Cameron takes part in a BuzzFeed News and Facebook live E.U. referendum debate in London on June 10. (Adam Gray/Buzzfeed News/Facebook/Agence France-Presse via Getty Images)

THE EUROPEAN Union is not popular just now. The E.U.’s median favorability rating in 10 major nations, encompassing 80 percent of its 508 million inhabitants, is a tepid 51 percent, according to a recent Pew Research Center survey. This is not surprising given the crises — economic, migratory and security-related — confronting Europe.

In the United Kingdom, the E.U.’s approval rating is an even lower 44 percent, even though Britain has opted out of Europe-wide institutions that euroskeptics most dislike — such as the common currency — and has negotiated other special exemptions from E.U. strictures. In this skeptical mood, British voters will go to the polls June 23 and choose whether to stay in the E.U. or begin a negotiated departure. “Brexit” would be the first such secession in E.U. history but, if successful, possibly not the last. The latest polls — taken before Thursday’s shocking assassination of Jo Cox, a pro-E.U. Labour Party member of Parliament, prompted a suspension of the referendum campaign — suggest British voters may well vote “leave.”

This would be contrary to the pleas of Prime Minister David Cameron, President Obama and practically every elected leader across Europe. It would be contrary to the internationalist example set by Ms. Cox, a committed and thoughtful campaigner for the rights of refugees and supporter of a vigorous British response to the Syrian war that has forced so many to flee.

It also would be dangerous for the world, for Europe and, not least, for Britain.

We understand the populist impulse behind the Brexit surge. Brussels and its multiple officious agencies are remote; their ponderous processes offer no prompt resolution to the issues that worry Britons most, including a surge of immigrants via the borderless E.U. That this impulse is understandable, however, does not make it any less, well, impulsive; there’s nothing particularly new, or particularly admirable, about the politics of anti-immigrant backlash. Any control Brexit would “take back,” to paraphrase the Leave campaign slogan, would be offset by increased economic uncertainty and political tension, to include conflict, potentially, with Scotland, which might rethink its recent vote to remain in the U.K. rather than join a flight from Europe. Brexiteers promise a boom born of deregulation; practical people grasp that Britain’s global financial center and export economy require regulation and standard-setting, including some that will inevitably be carried out multilaterally. Leaving the E.U. won’t change that reality, just render Britain less influential in shaping it.

For all its defects, the European Union is still a force for comity and commerce among the peoples of the continent, and a multiplier of their power and influence on the world stage. The E.U. is a strong partner with the United States, especially so when it includes Britain’s economy, the world’s fifth largest, and its military, the fifth most powerful . What’s more, it is a force for stability, possibly the most important of all the public goods that governing institutions provide — but, alas, the one most often taken for granted. Sensible citizenries prize stability as well as grievance and don’t lightly vent the latter at the risk of the former.

Come June 23, we hope the British people will vote accordingly.