Demonstrators take part in a march for a People's Vote in London in October | Niklas Halle'n/AFP via Getty Images Opinion Why the EU should fear a second UK referendum Europe has enough on its plate with Hungary, Poland and Italy.

Bad news for Theresa May is good news for the chances of a second Brexit vote.

With the British prime minster struggling to get her Brexit deal through parliament, more and more Europeans are hoping the U.K. will hold a second referendum and vote not to leave at all.

They should be careful what they wish for.

Since the 2016 Brexit vote, a number of European leaders have called the U.K.’s choice a “tragedy” and stressed that the British are always welcome back. The U.K. paid for a big part of the EU budget, and many saw it as a counterweight to Germany and France.

The U.K. should be welcomed back — but later, not now.

A vote to remain would leave millions of bitter Brexiteers feeling betrayed.

For anyone rooting for a stronger EU, there should be nothing more terrifying than the U.K. overturning its Brexit decision and simply staying in.

If the result of the second referendum goes against the first, millions of bitter Brexiteers will feel betrayed by an elite who promised them their initial vote would settle the Europe question for good.

Given the passions a second referendum would unleash — reigniting deep divisions between poorer and richer parts of the country — the U.K. would resume its EU membership as a nation — or, rather, a collective of nations — recovering from a profound sense of disruption, even trauma.

The last thing any British leader would do in a house so divided is contemplate any deeper entanglement with Europe. The U.K. would slow down or block essential EU reforms, seek to extract special favors, and ruthlessly use any available alliance within the bloc to protect a narrowly defined national interest.

And, of course, the U.K. would always be teetering on the brink of a new Brexit process. Brexit believers would not give up.

The intensity of their anger would be more than the consequence of being deprived of victory after being told there would be no further battle.

Three key European treaties — Maastricht, Nice and Lisbon — were rejected by Danish and Irish voters before being ratified, after crucial changes, in a second referendum. Ever since, U.K. voters have been fed the idea that a second vote amounts to a violation of democracy.

This antipathy to a second referendum fits into an English propensity to see politics not as a negotiation, but as a sport. To many, being asked to vote again feels as if the loser of the Wimbledon final would demand a rematch.

Only recently — and because it suited Remainers and many in Westminster — has a second referendum been no longer dismissed as a project that perverts the course of democracy.

Europe would welcome a change of heart by the U.K.

To be sure, the chances of a second referendum are still not exactly high. Theresa May still says she does not want one, and the obstacles are many. But there is a mounting groundswell to give people a say. And poll after poll suggests that if it comes to a new vote, Remain would be likely to win. If this happens, any U.K. government would immediately inform its partners that it’ll stay in the bloc.

The official reaction in Europe would be to welcome the Brits’ change of heart. No government and few citizens wanted the U.K. to leave in the first place.

They might even see, as an added benefit, the temporary muting of Euroskeptic forces agitating to “take back control” from Brussels. But the upsides won’t last long.

Looking for levers to stop closer EU-wide cooperation has shaped British policy for the best part of 30 years. Until 2016, this was an element of its strategic calculus, or an act of self-preservation for the ruling party of the day. But after the trauma of two bitterly fought referendums, shaped by visceral distrust of Europe, it would become an existential national priority.

Past performance of both Labour and Tory governments suggests that London would look for allies not just in Copenhagen or The Hague, but would seek them in Warsaw, Rome and Budapest as well.

Old EU hands will remember how former Labour prime minister Tony Blair traveled to Sardinia to cozy up to Silvio Berlusconi recovering from his latest hair transplant. Recently, the Tories have sought to shield Hungary’s authoritarian leader Viktor Orbán from EU measures challenging his ability to govern as he pleases.

For Europe, this couldn’t come at a worse time.

The surge of anti-establishment anger across the continent — largely a consequence of the financial meltdown a decade ago — confronts liberal democracies with a potentially existential threat. The violent Yellow Jackets protests in France show the storms of the past few years are far from over.

If the EU wants to ensure its survival, it will have to make far-reaching changes to the way it responds to migration, fights climate change and poverty, manages its security and common currency. For this, it must become easier to govern, easier to understand and more democratic.

The last thing the EU needs, faced with these huge tasks, is a traumatized U.K. using its power and diplomatic savoir-faire to freeze the EU in its present state. Its painful deadlock over Brexit may be diminishing the U.K.’s standing in Europe, but its diplomatic machine remains a formidable one. The U.K.’s soft power is probably unmatched for a mid-size country.

For the EU, tackling nationalism in Warsaw, populism in Italy, authoritarianism in Hungary is difficult enough. A U.K. working across the continent to fend off anything threatening its own brittle national cohesion could present the European Union with one of its most insidious challenges yet.

Thomas Klau is senior Europe analyst with Eurointelligence.