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British Prime Minister Theresa May's visit to the White House on Friday was always going to be more about optics than substance.

Here is the first world leader to call on President Trump — a Briton, a woman and a political conservative with a point to prove. And there is Trump, who has spent his first full week in office upending the status quo, clinging to conspiracy theories and falsehoods and confounding allies and enemies alike. He, too, may want to change the message.

The duo will preen about the renewal of the "Special Relationship," the phrase that clings like a barnacle to any discussion of British-American ties. They'll congratulate each other on last year's twin world-altering votes: Trump's shock election victory and Britain's approval of Brexit, a departure from the European Union that May initially opposed but now is entrusted to lead. If all else fails, they could fawn over the legacy of Winston Churchill, whose bust was restored to the Oval Office by Trump.

But beyond that, they will step into tricky terrain. May and Trump are not Reagan and Thatcher 2.0, no matter the British prime minister's own breathless allusions to the 1980s at a speech to Republican lawmakers on Thursday.

"May is everything that Trump is not: a careful, low-key and pragmatic member of the political establishment with a decades-long career in elective office," wrote the Post's London bureau chief, Griff Witte. "She holds mainstream positions on critical issues such as trade and security that put her sharply at odds with Trump’s protectionism and isolationism."

British Prime Minister Teresa May addressing Republican lawmakers in Philadelphia on Jan. 26. (Mark Makela/Reuters)

Facing a tough negotiation with Brussels over the terms of Britain's E.U. exit, May needs assurances over a favorable trade deal with the United States. She may get them from Trump in a soundbite, but the actual terms of any pact will only be sorted out as Britain gets closer to leaving the European Union. And hashing that out with the Trump administration — which has already announced numerous protectionist policies and has insisted upon being "America First" in every context — may be harder than it looks.

May's speech in Philadelphia to assembled GOP lawmakers pandered to Trump's populist narrative, praised the resurgent nationalism taking hold in both countries and hailed a Republican party that "swept all before" them in elections. She also did not have any meetings scheduled with Democrats, giving her trip an unusually partisan cast.

Yet in the same speech May also insisted on the importance of NATO — a military alliance Trump deemed "obsolete" — celebrated Britain's shared values with the European Union — whose unraveling Trump has cheered — and talked about the success of the nuclear deal with Iran — which Trump wants to tear up. She insisted on the distinction between radical extremists and hundreds of millions of Muslims who are adherents to a "peaceful religion," rhetoric you likely will never hear from Trump.

May, in effect, was defending a status quo Trump seems intent on dismantling.

"May’s strategy is clear," tweeted Shashank Joshi, a senior fellow at RUSI, a London-based think tank. "Embed the message in a pile of sycophantic schmaltz."

Not surprisingly, May's critics back home attacked her for "groveling" in front of Trump. Most people in the British political mainstream have been put off by the new American president and disturbed by his willful disregard for the institutions that uphold the Western liberal order. Over the past year, Trump's most visible ally in Britain has been the pro-Brexit agitator Nigel Farage, who remains a deeply polarizing figure on the fringe of his country's politics.

May's trip highlights the awkwardness of Britain's current place in the world. May can't sell Trump-style protectionism at home. She knows that Britain, a country of 60 million people, needs meaningful trade deals with the rest of the world in order to successfully detach itself from Europe. But her message of a "global" and "internationalist" Britain will fall on deaf ears at the White House.

"In the context of the newly developing U.S.-U.K. 'special relationship,' the very idea of 'global Britain' sounds bizarre," wrote Post columnist Anne Applebaum. "The U.S. president’s campaign made the word 'globalist' into an insult. ... May’s broader 'global' vision is doomed, at least as long as it is tied to a protectionist and isolationist U.S. president."

May's critics say the logical move in the face of Trump would be to turn closer to Europe by taking a leading role in shoring up NATO and countering Russia, a country whose ties to Trump alarm many European leaders. But the politics of Brexit mean she can't.

"The curious thing is that Brexit was supposed to be about taking back control: immunizing the country from foreign whim and interest, while asserting national dignity and independence," wrote the Economist this week. "Increasingly that looks like a bad joke."

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