It was hard to look at the two warring camps in the Brexit vote and not think of The Clash's 1982 classic "Should I Stay or Should I Go?".

Now that the United Kingdom has officially decided to go, it's almost impossible not to think about Donald Trump. And not just because Trump landed in (anti-Brexit) Scotland on Friday, as Great Britain woke up to its brave new world, and immediately tried to make the Brexit vote about himself:

I'm not being glib about the earthquake that just shook Britain and Europe's post-World War II Pax Europea. The U.K. and its leader — Prime Minister David Cameron or, more likely, whoever replaces him in October — have some big decisions and tricky negotiations ahead, and the EU's pending loss of its second-largest economy could upend the entire half-century experiment in European harmony. But Britain will work that out in due time, and the only answer they are going to get today is the one spoken by 52 percent of voters: "Leave."

America has its own big decision coming up, and if you are a supporter of Trump, Britain's decisive vote to leave the EU is glad tidings, a ray of sunshine after a few weeks of soupy London fog. If you don't want Donald Trump to be president, the Brexit vote is a wake-up call.

The first lesson Brexit has for anti-Trump America is that there's a potential majority out there that is angry, scared, and more than willing to jump into the abyss. Sober analysts and economists warned Britons repeatedly that pulling out of the EU would be an economic and security debacle. "They heard the warnings, listened to experts of every kind tell them that Brexit meant disaster, watched the prime minister as he urged them not to take a terrible risk," says Matthew d'Ancona at The Guardian. "And their answer was: Get stuffed."

It wasn't young people giving the finger to the experts, either. According to a YouGov poll, support for exiting the EU steadily rose with each age bracket, from 75 percent of those aged 18 to 24 wanting to stay, versus 39 percent for those 65 and older. If older Britons are proving less risk-averse than the young, there's no reason to think America's most reliable voters are immune to change fever. In many ways, Hillary Clinton represents a continuation of President Obama's policies, and Donald Trump inarguably represents change.

Great Britain is, technically, an island (or two), but the winds buffeting the U.K. don't stop at the water's edge. "The referendum came at a time when populist revolts against elites were gaining momentum, from Eurosceptic parties in France, Germany, Austria, and Scandinavia to Trump's brand of Republicanism in the U.S.," says The Guardian. "As ever," adds The New York Times, "referendums are not about the question asked but the political mood at the time, and the political mood is sour."

The second big lesson Brexit has for Trump opponents is that nativism, anti-immigration fervor, and elite-bashing are potent tools, not to be underestimated. There was a definite flavor of "Make Britain Great Again" running through the Leave campaign, with Brexit proponents arguing that British sovereignty was being undermined by unelected elites in Brussels. One reason the referendum passed is the unexpectedly strong support of working-class Labour voters in northern England, the rough equivalent of midwestern Reagan Democrats, who don't believe they have benefitted from open markets and open borders.

So "while leaders of the Leave campaign spoke earnestly about sovereignty and the supremacy of Parliament," says Steven Erlanger at The New York Times, "it was anxiety about immigration — membership in the European Union means freedom of movement and labor throughout the bloc — that defined and probably swung the campaign." The Leave camp urged Britain to "take control" of its borders. Instead of Mexico, the Eurosceptics pointed an accusatory finger at Turkey, which hopes to join the EU. In the hands of the U.K. Independence Party and its leader Nigel Farage — whose success in the polls pressured Cameron to call for the referendum in the first place — that anti-immigrant and anti-Muslim sentiment was not infrequently called racism.

The last red flag for those who don't want Trump to be president is that you can only trust the polls so much. Just about everybody who's anybody was in favor of staying in the EU — every living prime minister, the leader of Britain's two major parties, Obama and the leader of every other important ally, academics, business leaders, and celebrities — but a majority of everyone else said no. I mean, England ignored a plea from James Bond:

The polls before the referendum were close, and tightening, but most Britons went to bed Thursday night with the expectation that they would still be a part of Europe when they woke up. If the best polls got it wrong, it's possible that Britons were telling pollsters what all the cool kids were saying, not how they intended to vote. The American elite — Obama, academics, business leaders, celebrities, and even a good number of Republican opinion and political leaders — are wary or hostile to the idea of a President Trump.

Now, Vox's Ezra Klein makes the case for trusting the polls, noting that Trump led just about every poll in the GOP primary, but he inserts a note of caution, too. "Brexit's win doesn't predict Trump's victory, contrary to some of the chatter I've seen on Twitter," he says. But "when evaluating the likeliest outcomes, look to trustworthy polls rather than your gut. Hillary Clinton's 7-point lead over Donald Trump still makes her the favorite, but if those numbers flip, take it seriously. Pundits who stick to their priors even when the data tells them to abandon ship are not faring well this year."

It's worth remembering that when David Cameron agreed to the EU referendum three years ago, even though he opposed leaving the EU, he assumed that it had little chance of passing. Leaving the EU was "caricatured as an obsession of very rightwing Conservatives," as The Guardian puts it, but caricatures can deceive those who believe them.

All it took to bring the idea of a Brexit to the mainstream was a wealthy, colorful, New York–born, media-savvy, purposefully outrageous, peculiarly coifed, self-aggrandizing, selectively conservative, populist politician named Boris Johnson. The former London mayor was once an ally of Cameron, a fellow Tory. Now that his successful leadership of the Leave campaign has pushed Cameron out of office, he might well be Britain's next leader. If that can happen in Britain, America isn't safe from Donald Trump.