Early on the morning of Nov. 9, Republican President-elect Donald Trump addressed supporters in New York, declaring victory over Democrat Hillary Clinton. Here are key moments from that speech. (Sarah Parnass/The Washington Post)

DONALD TRUMP was elected the 45th president of the United States on Tuesday. Those are words we hoped never to write. But Mr. Trump shocked the pollsters, riding a wave propelled in part by rural and Rust Belt voters who felt the political establishment had cast them aside. While Mr. Trump might not have done the same for his rival, Hillary Clinton, had she won, all Americans must accept the voters’ judgment and work for the best possible outcome for our country and the world.

What does that mean in practice? First, to hope that Mr. Trump will be a better president than we fear, and to support him when he does the right thing. Mr. Trump will soon command a sprawling federal bureaucracy, sophisticated law enforcement and intelligence agencies, and the world’s most powerful military. We have every wish that he will understand that the U.S. system of government is not for or about one person. He alone cannot fix it. The powers of the Oval Office do not exist to punish his enemies,something he mused about as the campaign drew to a close, according to a recent New York Times article.

The new president will face immense and unrelenting challenges from Day One. He inherits a world in which liberal democracy is in retreat and U.S. leadership is doubted. The Middle East is in turmoil, North Korea’s nuclear arsenal is growing, Russia and China are flexing their muscles. At home, President Obama bequeaths an economy in generally good health but facing problems: slow growth, stubborn inequality, long-term stress on the federal budget.

We can’t pretend to optimism that Mr. Trump will suddenly shape more rational responses to these problems than he offered on the campaign trail, nor that he will discover a discipline or wisdom he has yet to display. Over the course of his campaign, Mr. Trump spoke about jailing Ms. Clinton, suing women who accused him of unwanted sexual advances, neutering the speaker of the House and revoking press freedoms. Per the Times article, he has spoken of creating a super PAC dedicated to political vengeance. He has promised to deport millions, rip up trade agreements, apply religious tests and sabotage international efforts to fight climate change, each of which would hurt many people.

The Fix's Peter W. Stevenson explains how Donald Trump beat expectations – and Hillary Clinton – by winning key swing states, and turning a few blue ones red. (Peter Stevenson/The Washington Post)

If he attempts to act on these goals and inclinations, others must rally to the defense of constitutional principles and sound government. Republican leaders in Congress endorsed Mr. Trump on the bet that he would back their legislative agenda and respect their authority. They will be put to the test. Law enforcement agencies must guard against any attempt to use them unlawfully. The judiciary, the civil service, the media and civil society more broadly will have important roles to play.

Americans are not and have never been united by blood or creed, but by allegiance to a democratic system of government that shares power, cherishes the rule of law and respects the dignity of individuals. We hope our newly elected president will show respect for that system. Americans must stand ready to support him if he does, and to support the system whether he does or does not.