It is an unscientific but observable law that the more important an era is, the more dangerous it is. There is, quite simply, more to be won or lost in such times. In this sense, the two great liberal democracies of the modern era—Britain and the United States—are now living through their most important periods in generations. While Donald Trump could be elected U.S. president before the year is out, on June 23 the British people will vote to decide whether Britain will leave the European Union.

This decision comes at a time when Europe is facing extreme pressures; from the rise of far-Right parties to the growing influence of Islamism to the migrant crisis, all of which threaten the political and social stability of the continent as a whole.

But what would Britain leaving the EU—the so-called “Brexit”—mean for the country’s and Europe’s Jews?

There is an argument to be made that Brexit would be good for the Jews because it would distance them from an increasingly anti-Semitic continent. This argument would be wrong. It will undoubtedly put the whole of European Jewry at greater risk.

For centuries, savage, backwards, reactionary, and violent anti-Semitism was the norm in Europe. The last several decades are the exception. If Britain leaves the EU, this could change. Fringe movements whose main goal is Brexit—like the United Kingdom Independence Party (UKIP), a conglomeration that contains racists and anti-Semites of all kinds—will be empowered, and their bigoted policies could threaten to become mainstream. These once-marginalized extreme forces, whose advocacy for Brexit is in reality about immigration and hostility to minorities, will have scored a victory of dangerous precedent. And this is a pan-European problem. With one of Europe’s three major nations no longer in the EU, other far-Right, anti-EU, and anti-Semitic forces across the continent, from Marine Le Pen’s Front National in France to Hungary’s Jobbik party, would receive a boost from the example of a leading country’s exit. At its heart, most anti-EU sentiment is populist sentiment, with all the prejudices that this has always carried. Just today, Labour MP Jo Cox, who was campaigning for an “In” vote, was killed by a man who reportedly shouted “Britain First” (an anti-EU far right organization) as he shot and stabbed her. The EU is seen as aloof and unaccountable: run by a small, unelected cabal of (mostly foreign) people that dictates the lives of the ordinary, hardworking man. Sound familiar?

Brexit is something the greatest geopolitical danger facing the EU today, Russian President Vladimir Putin, desperately wants. He sees the EU (as he does NATO) as a serious threat to Russian power and influence. His pervasive funding of anti-EU, far Right parties shows his clear desire to see the union collapse. Putin’s revanchist Russia, which has re-introduced Orthodoxy—with the centuries of anti-Semitism it has carried with it—as a main staple of national identity, bodes ill. A Europe with a more influential Russia would be a more anti-Semitic one.

There are genuine arguments to be made against the EU. It is bloated and in part corrupt, and does infringe on national sovereignty to a degree, though not nearly as much as its critics claim. But it is also a stabilizing force that has kept Europe peaceful, and thus safe for the Jews, for almost half a century. A Europe with a weakened EU would undoubtedly start to fragment politically and socially. This fragmentation would, over time, empower various reactionary forms of nationalism across the continent.

More immediately, Brexit would mean that the UK can no longer be an easy refuge for continental Jews whose lives are far more difficult. The UK has its problems, but it remains the best place in Europe to live as a Jew. In the last year alone, just under a thousand French Jews have arrived in London, fleeing anti-Semitism. Things may well get even worse, and without the EU’s free movement laws, the Jews would be forced to seek asylum or face a points-based entry system.

Then there is the security issue. Jihadist, anti-Semitic murders of the type seen in France and Belgium over the past two years are today’s major security threat. Jewish buildings across Western Europe are now guarded, if not by the army, then by police carrying military-grade weapons. As several leading British intelligence and military chiefs have said publicly, remaining in the EU is the best way to combat Islamist atrocities. Intelligence sharing is vital. Terror is a transnational problem requiring transnational solutions. Brexit would be a hazardous step backwards.

Within European politics as a whole, Euroscepticism is part of the popular political landscape, but the political elites of many EU states just don’t listen. This means the anti-EU argument—especially concerning immigration—is left to parties like the Front National to articulate, along with their other more extreme positions. In the UK, by contrast, Euroscepticism is deeply rooted within mainstream parties (as well as UKIP-type entities) that lack the quasi- (or often outright) fascism of Europe’s other anti-EU parties. By remaining in the EU, the UK has an opportunity, possibly a unique one, to lance that boil.

If Britain stays in the EU, it can lead the moderates and the pragmatists at the European level and oppose the political “skinheads.” And the skinheads have always, always, been bad for the Jews.

David Patrikarakos is a contributing editor at the Daily Beast and the author of Nuclear Iran: The Birth of an Atomic State. He tweets @dpatrikarakos.

[Photo: Mike Gimelfarb / Wikimedia]