LONDON — Britain stepped into the unknown on Wednesday — and possibly off a cliff.
On a day that blended dull ritual with undeniable historic import, Britain formally began its departure from the European Union with the delivery of a letter to Brussels, followed by lofty words from Prime Minister Theresa May in Parliament. Two years of grinding divorce negotiations now begin, with the outcome unclear, except that the talks are certain to be contentious and spiteful — and that the only sure winners will be lawyers and trade negotiators.
For the first time, the European bloc is losing a member, not to mention its second-largest economy. The multilateral architecture that has shaped the Western world since the aftermath of World War II has taken a severe blow, and questions abound about whether this pivot toward nationalism and self-interest marks the beginning of a more volatile global era.
When Britons voted last June to leave the European Union, the champions of “Brexit” argued that the country, by leaving, was at the front edge of a larger populist wave. Months later, the election of Donald J. Trump as president of the United States only deepened the feeling that an anti-establishment political contagion was sweeping across Western democracies, upending the established order. Britain, the argument went, would be a winner in this new era.
Few people predicted the British exit, and fewer still predicted Mr. Trump’s victory. But few predicted where things stand now, either: The European Union, if still ailing and dysfunctional, is far from dead. Populist parties are sinking in the polls in Germany and underperformed in the Dutch elections this month. Opinion polls in many countries show continued public unhappiness with the bloc but little desire to see it fall apart.
“No one is following Britain out of the E.U.,” Pierpaolo Barbieri wrote recently for Foreign Affairs, a magazine published by the Council on Foreign Relations, a nonpartisan research group.
The question now is whether some Europeans, having watched the first aftereffects of the vote to withdraw and the American presidential vote — political division in Britain and the fall of the pound, and political missteps in the Trump White House — are sobered by the chaos of the right. That thesis is speculative, too, and will be tested next month in France, where the traditional parties have imploded and the far-right nationalist Marine Le Pen, if victorious, has promised to take France out of the European Union. But for now, Emmanuel Macron, who is pro-Europe, is leading the polls.
Picking winners at such a volatile moment is perilous, but many analysts agree that the British withdrawal, and the uncertainty it produced, has been good news for Russia, and possibly for China, as two large powers that can exercise greater leverage in negotiations with individual European capitals than with a tightly unified European bloc that, taken together, is a geopolitical powerhouse.
“ ‘Brexit’ surely strengthens the disintegrative processes already underway in the E.U., and therefore is a boon to a Russia,” said James Nixey, head of the Russia and Eurasia program at the London-based think tank Chatham House. “The E.U. is more powerful than any single actor, even Germany, so anything that diminishes a rival in the zero-sum terms in which Russia thinks strengthens the Russian voice in Europe.”
Britain’s absence at the European table could also help the Russian president, Vladimir V. Putin. Partly pressed by Britain, the United States’ main ally, the European Union has been tough on Russia over its annexation of Crimea, and the bloc has moved to cut Europe’s dependence on Russian natural gas. Anything that shifts power in Brussels away from that Anglo-Saxon view is considered a plus for Moscow.
The coming exit from the European Union has already turned Britain inward, with the government and the country’s powerful tabloid news media fixated on the particulars of its withdrawal: the uncertainties of whether the country will maintain access to the bloc’s single market; demands that the country take control of its borders to stunt immigration; and an insistence on “reclaiming sovereignty” by returning lawmaking powers to London.
Those themes of national sovereignty and curbing immigration resonate across the Continent, which is why some saw the British exit as a political precursor and the European Union as an endangered species.
In December, however, Austrians narrowly elected a pro-European president, Alexander Van der Bellen, over Norbert Hofer of the far-right Freedom Party. In Spain, the populist Podemos party underperformed polling expectations last year and the conservative prime minister, Mariano Rajoy, stayed in office.
This month, the Dutch gave the far-right anti-European politician Geert Wilders fewer votes than expected in a northern European country similar in its political outlook to Britain. In Germany, Chancellor Angela Merkel remains popular in the polls, although weakened by her long service in the job and by severe criticism of her 2015 “open-door” immigration policy. The anti-euro, anti-immigration Alternative for Deutschland is slipping, however, and Ms. Merkel’s main challenger is the pro-European Martin Schulz of the Social Democrats, the former head of the European Parliament.
Even Bulgaria, the European Union country considered most influenced by Russia, saw voters endorse the pro-Europe, center-right party in elections last weekend.
As European voters seem to be tentatively endorsing unity, Britain is confronted with widening divisions. On Tuesday, less than 24 hours before the exit letter was delivered to Brussels, the Scottish Parliament voted to demand a new referendum on independence from the United Kingdom. Such a referendum is unlikely to happen anytime soon — it requires the approval of the British government in Westminster — but the rising nationalism in Scotland is a reminder that London could get a taste of its own medicine.
With her government desperate to maintain Britain’s standing in the world, Mrs. May has turned to President Trump. He and his chief political adviser, Stephen K. Bannon, are deeply skeptical of multilateralism, free trade and “entangling alliances.” While NATO may pass muster as a security shield (provided everyone pays up), the European Union, like the United Nations, seems an example of the world that Mr. Trump and Mr. Bannon want to dismantle or, at the very least, weaken.
Yet Mrs. May has also tried to present Britain as committed to globalization and to global trade — as, effectively, still open for business. It is a tricky circle to square, demonstrating how difficult it is to predict Britain’s future. Some envision the country’s fate as being a European equivalent of Singapore, sovereign and respected, a partner eagerly sought by the rest of the world. Others warn that Britain could be left much more isolated than it is now, especially since European leaders feel they must strike a hard bargain.
“There is a political imperative that ‘Brexit’ not be seen as a success,” said Mark Leonard, director of the European Council on Foreign Relations, “because every government in Europe is challenged to some degree by resurgent nationalists who would be encouraged and inspired by a ‘Brexit’ success.”
For those British lawmakers in favor of the withdrawal, like Jacob Rees-Mogg, a Conservative legislator, the exit “is a wonderful liberation for my country.”
The single market, he told Prospect magazine, “is a bureaucratic, highly regulated means of making British business more inefficient — it’s about having a closed, inward-looking Fortress Europe approach, rather than engaging with the world.”
There is “no political event in my lifetime that has been better or more exciting for the nation,” he added.
But Mr. Leonard has his doubts.
“Britain may be sailing off to sea,” he said, “but the welcoming arms won’t be that numerous.”