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Column: Why the U.S. dreads a ‘leave’ win in the U.K.

One word sums up the feelings of U.S. policymakers today, as British voters decide whether to leave the European Union: alarm.

It’s the foreboding of watching a trusted, lifelong friend — the one you’ve relied on to have your back through any financial or personal crisis — about to leap into a messy divorce.

You fear your friend won’t be there for you, at least not for a while.

READ MORE: What is Brexit? 8 reads on Britain’s big choice

“If Brexit happens, we won’t be able to count on 10 Downing to focus on the agenda we share — how to deal with Syria, Russia or ISIL, or the crises in a Europe,” a senior U.S. official told me. “They’ll be consumed by untangling the mess involved in what it would actually take to leave the EU.”

There are U.S. economic consequences at stake, too, of course. A victory for the “Leave” forces would roil world financial markets. And it would force expensive changes for thousands of U.S. businesses, from Caterpillar to Ford, who created UK hubs as their gateway to the single, tariff-free market of the 28-nation European Union.

But the feelings this Brexit vote has stirred among American officials go much deeper than that. The much-touted “special relationship” between the globe’s two largest Anglo-Saxon nations isn’t just a cliche. It speaks to the level of trust, shared values and similar world views that have supported America’s most muscular and active alliance since it entered World War II on Britain’s side in 1941.

This relationship was the cornerstone of the NATO alliance against the Soviet Union during the Cold War. There were differences, during the Vietnam War, and in the Middle East. But the cooperation far outweighed those moments, especially after the romance that blossomed between Ronald Reagan and Margaret Thatcher in the early 1980s.

As two Cold Warriors, Thatcher supported Reagan’s toughness toward the Soviet Union. Washington backed Britain in the Falklands War despite qualms. Thatcher encouraged President George H.W. Bush to intervene militarily after Iraq invaded Kuwait in 1990. “This is no time to go wobbly, George,” she famously said to him in a phone conversation, showing a level of intimacy unusual between two world leaders. (Dick Cheney later dismissed that as an “old wives tale,” but Thatcher’s memoirs document the phone call and the phrase.)

In this century, after 9/11, British troops were all-in when NATO joined the U.S. in its 2001 invasion of Afghanistan to rout al-Qaeda. London did likewise for George W. Bush’s invasion and lengthy occupation of Iraq in 2003, despite the British public’s rapid disenchantment with the venture.

“When there are tough choices to be made, we can count on London to have our back, and vice versa,” said a recently departed administration official. “And without it? Just look at what happened when London didn’t come through on bombing Syria. President Obama flinched.” She was referring to President Obama backing off his threat to bomb Syria over its use of chemical weapons, after the House of Commons in August 2013 refused to authorize British involvement, prompting Prime Minister David Cameron to demur. President Obama made the same decision 11 days later.

President Obama cared so deeply about the outcome of today’s vote that he traveled to London in April, and standing by Cameron, warned of the consequences to Britain’s economy and to the world. In an unusual intervention into a domestic political issue, Mr. Obama told the British public that EU membership “makes you guys bigger players,” and that when it comes to forging trade deals, a UK flying solo “is going to be in the back of the queue.”

Washington’s alarm may be overstated. The shared values, and intense intelligence cooperation, will continue. But it’s a question of focus. This president and the next will want an undistracted British ally in wrestling with the crises ahead: the Islamic State and terrorism, Russian adventurism, a Europe beset with a migrant crisis and fraying economies, and an increasingly belligerent North Korea.

Not surprisingly, there is a political angle, too. Among the ranks of senior U.S. diplomatic and national security officials appointed by a Democratic president, there’s dread at the thought that Britain’s populist, anti-immigration, anti-trade political forces could prevail. “Nationalism has been rearing its ugly head in mainland Europe for years, decades — but now in Britain, too!” one exclaimed. “It would be a troubling sign about where the world is trending. And maybe here, too.” The reference to Donald Trump was unmistakeable.

The polls don’t close in Britain until 10 p.m. there, with full results not expected until early Friday morning, London time. This is one overseas election worth staying up for the late returns.

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