Donald Trump has won. Now we have to fight him.

Take it from a Brit: I know how bad a crushing electoral defeat like this can be. I went through one in June. And Donald Trump is going to cause enormous harm to America’s standing both domestically and internationally. He’s in charge of appointing Supreme Court justices, just for starters. In the worst-case scenario – and we’re all learning to start paying attention to worst-case scenarios – he could rashly precipitate a global thermonuclear war.

So let’s not minimize the downside of a Trump presidency. But at the same time, it’s downright un-American to simply descend into utter despair. The noble action, in the face of adversity, is to fight, and never give up, and, ultimately, to overcome.

And here’s the first piece of good news: Trump’s presidency, unlike Brexit, has an end. Trump is a temporary phenomenon, with a tendency to self-destruct; there’s a chance he won’t even last four years as president.

On top of that, as Republican lawmakers have been reminding us for the past eight years, American democracy comes with a lot of checks and balances. Extreme times call for extreme measures. Republican filibusters, and refusals to confirm presidential appointments, have been extremely harmful – but turnabout, in this unique case, is definitely fair play. Democrats now have control of the playbook that the Republicans wrote, and they had better use it to its fullest extent.

The fight continues outside the Beltway, too. Hillary Clinton won a majority of the popular vote, including a large number of #NeverTrump Republicans. The mandate for a robust opposition is clear, and Trump is so beyond the pale, on so many different axes, that it will be incredibly easy and natural for a very large and very powerful part of the United States to coalesce into an unyielding stance of opposition to anything and everything that Trump attempts to do. Trump’s anti-trade stance will effectively alienate big business and Wall Street; his authoritarianism will make him uniquely hated by the press; his ugly racism and misogyny will render him utterly unsympathetic to anybody who believes in basic principles of equality and fairness.

As Barack Obama has learned, it’s hard to govern America even when you have a broad base of elite support. Without that base, Trump is going to find himself to be one of the weakest presidents in living memory.

And it’s not just the United States where the elites will be aligned against Trump; it’s the world. (The non-Russian world, anyway.) Trump loves to look at the world in a zero-sum way: he always considers an unhappy counterparty to be a sign of success. But without the support of our allies, America will be able to achieve almost nothing internationally, even as a Britain-free Europe seeks to become more politically unified and more economically powerful. NATO will see its center of gravity move significantly eastwards, towards Europe and away from the U.S., which will not necessarily be a bad thing.

The Brexit vote in Britain was a nihilistic vote for irrelevance, and the Trump vote in the US is not so different. But nature abhors a vacuum, especially one the size of America. Trump will be fought politically, he will be protested nationally, and he will be opposed internationally. He will spend his entire presidency on his back foot, until he is no longer president, and a breath of fresh air can enter the White House. All it takes is the courage is to oppose him, the resolve to avoid defeatism, and the determination to continue the fight no matter what. The arc of the moral universe is long, but it bends towards justice. This is not the end. Not unless we let it be.