A toxic political brew is percolating around the UK's decision Thursday to leave the European Union, a fateful vote with consequences not just for America's closest historical ally but for Western stability that could trigger economic and political reverberations in the United States.

While the vote is designed to settle Britain's long-ambivalent attitude toward Europe, the underlying themes of the referendum look familiar to anyone who has been transfixed by the turbulent U.S. presidential election.

The similarities in the two campaigns suggest powerful shared tensions are tearing at the world's most enduring English-speaking democracies. The forces unleashed seem likely to rattle the respective political systems for years to come.

They both feature a torrent of populist anger, fear-mongering by politicians, hostility toward distant elites and bitterness toward the ruling political, media and business establishment.

In the U.S. and the UK, emotion and hyperbole have become a constant undercurrent of politics and are being used as a weapon by politicians in both camps, right and left, "Leave" and "Remain."

Former London mayor Boris Johnson warned in May that the E.U. was the latest manifestation of a 2,000-year project to unify Europe under a single government.

"Napoleon, Hitler, various people tried this out, and it ends tragically," Johnson told the Sunday Telegraph in arguing for leaving the European Union. "The EU is an attempt to do this by different methods."

Such emotive rhetoric is reminiscent of Trump's own claims that the independence of the United States itself is under threat.

"We will no longer surrender this country or its people to the false song of globalism," Trump said in a major foreign policy speech in Washington in April.

Palpable voter anger

And among voters, the anger is palpable in both countries.

In the United States, clashes have broken out between supporters and opponents of the presumptive Republican presidential nominee, while the debate is as coarse as it has been in living memory.

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In the United Kingdom, politicians of all sides were shocked by the killing of pro-Europe lawmaker Jo Cox of the Labour Party on Thursday. The man charged with her murder said when asked his name at a court appearance on Saturday: "Death to traitors, freedom for Britain."

In Britain, as in the U.S., the atmosphere has been particularly soured by an emotive debate about a wave of migration from the south and a perception that newcomers threaten the ethnic and political characteristics of each nation.

And at the center of both the referendum and the U.S. presidential election is the idea that the political status quo is not working for voters and that elected leaders are either incompetent or not listening.

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"On the one hand, we have disenchantment with elites," said Nicholas Dungan, a leading expert in European politics with the Atlantic Council. "On the other hand, it seems extraordinarily difficult for the elites to actually get anything done. The reason people are upset with the leadership class is not because of their leadership, it's because of their lack of leadership."

Professor Robert Tombs of St. John's College, Cambridge University, said many U.K. voters are frustrated that politicians don't seem to be listening.

"There is a sense that people feel that standard centrist politics is no longer representing them, and that has meant membership (in) political parties, and the proportion of people voting all over the Western world, has fallen," said Tombs, author of the book "The English and Their History."

He continued, "There is a sense that politics no longer matters, or that the people who run mainline politics are no longer in contact with the people who vote for them."

In the United States, that has enabled Trump to muster grassroots fury to stage a hostile takeover of the Republican Party. It also fed the "political revolution" ignited by Democratic presidential candidate Bernie Sanders, motivated not just by anger against Washington politicians but another form of elites: Wall Street titans.

The frustration runs particularly deep in Britain, where anti-Europe voters are not just motivated by fury toward members of Parliament but the regulations drafted by faceless bureaucrats in Brussels who execute EU policies -- and whom they cannot kick out of office in an election.

Strains of nationalism

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There is also a current of nationalism at work. It's not unusual, for instance, to see both Eurosceptics and Trump supporters utter the phrase: "I want to take our country back."

In each country, such feelings have translated to hostility toward outsiders.

In Britain, immigrants from struggling Eastern European states willing to work for low wages have become targets in a nation, like the U.S., in which globalization has badly hit heavy industry.





Brexit: What will immigration look like if Britain leaves the EU?



In the United States, Trump has accused undocumented migrants, most of them from Latin America, of undercutting U.S. workers. Trump has also slammed foreign actors like China and Japan for fleecing the U.S. in trade deals. The immigration question has been exacerbated by the flows of refugees from Middle East wars into southern Europe and opposition to the core E.U. principle of free movement of peoples between member states.In the United States, Trump has accused undocumented migrants, most of them from Latin America, of undercutting U.S. workers. Trump has also slammed foreign actors like China and Japan for fleecing the U.S. in trade deals.

Similarly, Eurosceptics have argued that, freed from the constraints of the European Union, British companies will be more competitive.

There is also the unconventional populist appeal that figures leading the establishment critiques have cultivated by expressing both their personalities and previously taboo sentiments.

In the United States, unorthodox outsiders like Trump and Sanders have left opponents -- like the entire Republican presidential field and Democratic presumptive nominee Hillary Clinton -- flat-footed.

Britain has its own colorful political characters -- most prominently Johnson, who like Trump, operates from beneath an improbable edifice of blond hair. The former London mayor grabbed a leadership role in the Brexit campaign that many observers see as positioning to become the next prime minister.

And UK Independence Party leader Nigel Farage last week sparked outrage among opponents by posing in front of a poster that suggested waves of brown-skinned immigrants were poised to swamp Britain, recalling Trump's labeling Mexican illegal immigrants criminals and racists.

A personality gap

Those leading the pro-Europe "Remain" campaign in Britain struggled to match the personality of the exit camp. Conservative Prime Minister David Cameron, despite winning the election last year, is mistrusted by many voters. Labour Party leader Jeremy Corbyn doesn't even enjoy majority support among lawmakers of his own party and is viewed as too left-wing by many others.

And the American president also has not seemed successful in moving British sentiment: In London in April, President Barack Obama made a personal appeal for the UK to stay in the EU that did not seem to register in polls.

For Trump, Brexit is one more policy on which to oppose Obama. The billionaire businessman expressed support for the "Leave" side last month.

"I think maybe it's time, especially in light of what's happened, with the craziness that's going on with the migration, with people pouring in all over the place," Trump told "Good Morning Britain" on ITV in March.

While no one knows how the referendum will turn out, there is one thing that everyone in Britain agrees on -- the referendum is the most important election in years.

And it is a vote that splits the U.K. Scotland and Northern Ireland are generally seen as more pro-Europe, while England -- with the exception of London -- and much of rural Wales are seen as harboring majorities in favor of Brexit.

There is at least one more common ideological similarity between the U.S. and UK.

Leading British Conservative Michael Gove, who broke with his boss Cameron to support leaving the EU, suggested that the United States is a model for the independence and self-determination the Brexit forces desire.

"The ability to choose who governs us, and the freedom to change laws we do not like, were secured for us in the past by radicals and liberals who took power from unaccountable elites and placed it in the hands of the people," Gove wrote in a personal statement explaining his position in February.

"Like the Americans who declared their independence and never looked back," he continued, "we can become an exemplar of what an inclusive, open and innovative democracy can achieve."