By Griff Witte, Anthony Faiola, Michael Birnbaum, The Washington Post

LONDON – The man who stands a reasonable chance of becoming the next president of the United States is “a hate preacher.” He is “unfit to hold the office” because of his “stupefying ignorance.” His pattern of reckless behavior inspires “a retching feeling.”

Those are not the words of Republican nominee Donald Trump’s domestic political opponents, eager to take him down in the rancorous home stretch of an almost incomprehensibly acid American election.

Instead, they are the sentiments of Washington’s closest allies, who, gazing across the Atlantic, have broken with decades of precedent that calls for studious silence and openly taken sides in a U.S. presidential election.

From the Baltic Sea to the Mediterranean coast, the prospect of Trump taking control of the world’s greatest power has triggered widespread anxiety in European capitals. It has also brought periodic outbursts from leaders who no doubt hope, perhaps in vain, that the views of America’s foreign friends will somehow make a difference among American voters.

But what Trump’s rise hasn’t done is prompted European allies to get ready for the possibility that he could actually win.

“They are taking it seriously,” said Xenia Wickett, head of the Americas program at the London-based think tank Chatham House. “But I don’t think they’re preparing for it.”

That lack of preparation leaves Europe dangerously exposed should Trump find a way out of the maelstrom generated by his vulgar comments in a 2005 video and pull off an unexpected victory over Democratic nominee Hillary Clinton in next month’s vote.

Europe is already at a vulnerable moment even without a White House resident who has called the most basic tenets of the trans-Atlantic alliance into question, and whose coziness with President Vladimir Putin comes as Russia has made a habit of menacing its weaker European neighbors.

Across the continent, populist movements that share much with Trump’s nativist nationalism are on the rise. Britain is on its way out of the European Union. The continent’s ability to hang together amid problems ranging from the refugee crisis to terrorism is being tested daily.

But a Trump victory could be the biggest challenge of all, forcing European nations to bind together to compensate for a likely American turn toward isolationism.

Even if Trump opted to maintain the traditional U.S. role as guarantor of European security, his extreme positions may prove so anathema that Europe would have little choice but to distance itself from Washington, said Wickett, a former U.S. National Security Council official under President George W. Bush.

“America would no longer be a country that you would necessarily want to be partnered with,” she said.

That shift has already been telegraphed through the scathing words of top European officials – words that could make it difficult to reconcile with Trump if he wins.

German Foreign Minister Frank-Walter Steinmeier in August called Trump a “hate preacher” who had much in common with Brexit backers and with the German far right. He said they were linked by their exploitation of fears to achieve political goals. This was “incendiary for society,” Steinmeier said.

Steinmeier’s boss, Chancellor Angela Merkel, has been more circumspect, though she has left little doubt about her true feelings. She has heaped praise on Clinton’s “strategic thinking” and commitment to the trans-Atlantic partnership.

“Whenever I had a chance to work with Hillary Clinton, it has been a great pleasure,” Merkel told the German newspaper Bild.

As for Trump, all she would say was that she doesn’t “know him personally.”

Neither, presumably, does French President François Hollande. But that didn’t stop him from saying that Trump’s “excesses” had given him “a retching feeling.”

Britain’s Parliament has even gone so far as to debate whether Trump should be banned from the nation’s shores. The January session yielded no action, but did exhaust the thesauruses of dozens of lawmakers who struggled to creatively convey just how much they disliked the real estate tycoon.

“Demagogue,” “buffoon” and “wazzock” – a semi-obscure Britishism meaning, roughly, “twit” – were among the insults that echoed off the drafty stone walls in the mother of all parliaments.

There’s little evidence that Trump’s reputation in Britain has improved since then, even though he, unlike Clinton or President Obama, backed the winning side in the country’s June Brexit referendum.

Trump has called himself “Mr. Brexit,” an apparent allusion to his belief that he can shock the world with victory much in the way anti-E.U. activists did in the referendum.

The most bombastic of those activists, longtime U.K. Independence Party leader Nigel Farage, has become a highly visible Trump ally. Farage spoke at a Trump rally in Mississippi in August, and was Trump’s guest at Sunday’s debate.

Trump has found other friends in the ascendant populist movements of Europe, including Hungarian Prime Minister Viktor Orban.

Orban, who built a razor-wire fence along the country’s southern border to block refugees and migrants from entering the country last summer, has hailed Trump’s proposals to crack down on terrorism. “I myself could not have drawn up better what Europe needs,” Orban said in July.

But Orban’s stand places him firmly in the minority among European leaders. For other nations, particularly the four NATO members that border Russia, Trump is the source of deep, almost existential anxiety.

The Republican nominee has gone back and forth over whether he would come to the aid of U.S. allies if they were attacked, even as Russia has staged provocative military drills and air incursions in the two years following its annexation of Crimea from Ukraine.

Three of Russia’s NATO neighbors – the Baltic nations of Latvia, Lithuania and Estonia – are together smaller than Missouri and stand no chance of defending themselves in the event of a Russian invasion. In that context, comments from top Trump adviser Newt Gingrich that “Estonia is in the suburbs of St. Petersburg” shook many in the region who have long counted Republicans as their staunchest advocates.

Concern over Trump runs so deep that Latvian lawmakers have started to reach out to Republicans in Congress, eager to build support among a constituency that might be a forceful counterweight to the would-be president’s isolationist impulses.

Ojars Kalnins, chairman of the Latvian Parliament’s Foreign Affairs Committee, said Latvian lawmakers were in talks with Senate Majority Leader Mitch McConnell, R-Ky., and Sen. Tom Cotton, R-Ark., to lead a delegation of Baltic politicians that hopes to speak in front of a Senate committee during the lame-duck session of Congress.

“The Trump comments and the Gingrich comments did prompt us,” Kalnins said. “It was a realization that people aren’t as attuned to the Baltic states as they used to be.”

But those modest steps are about as far as Europe has gone to prepare for a Trump presidency. The prevailing strategy for many diplomats and politicians is to hope he doesn’t win, and if he does, to simply wait and see what he will actually do, given his often-contradictory statements.

Some European analysts believe Trump’s foreign policy ideas are so radical that he would have trouble stocking the government with enough people committed to carrying them out.

“We expect there would still be cadre diplomats, a lot of people who are not showing the opposition flag to Trump but who are the safe tier of professionals,” said Juri Luik, a former Estonian foreign and defense minister who runs the International Center for Defense and Security in the Estonian capital Tallinn.

But Luik also cautioned that Europeans “shouldn’t kid ourselves” and noted that in the United States, the president calls the shots on security policy.

Indeed, far from being reassured, European leaders have often gone out of their way to stress just how worried they are.

“Trump is not only a problem for the EU, but for the whole world,” European Parliament President Martin Schulz recently told the German weekly Der Spiegel. “If a man is sitting in the White House . . . with no clue and describes expert knowledge as elitist nonsense, a critical point has been reached: Then an apparently irresponsible man is in a position which requires the highest sense of responsibility.”