There is plenty of democratic energy behind these movements. But because populists like President Trump value only the support of a narrow segment of citizens and claim an exclusive right to speak on behalf of “the people,” they are a real danger to the norms and institutions that are necessary to sustain democracy.

Like Mr. Trump, democratically elected dictators have often believed that they don’t owe political consideration to the minorities they vilify. And like Mr. Trump, they have often claimed that all those who challenge their rule — independent judges, critical journalists — are enemies of the people. For anybody who has studied how democracies die, the president’s dark rhetoric sounds familiar.

One of the things I most admire about the United States is its fierce attachment to the Constitution. Americans have as deep a commitment to democratic institutions, and as active a civil society, as the citizens of any other country in the world. If the defenders of democracy don’t make it here, it is doubtful that they will make it anywhere.

But one of the things I most fear about the United States is that the veneration of the Constitution is always in danger of turning into complacency. While the country’s system of checks and balances gives Americans the tools to safeguard their freedoms, the Constitution cannot defend itself. The defenses it puts in place will work only if citizens are prepared to use them.

As this realization dawned on many Americans in the past months, and a valiant fight for the soul of the country got underway, I felt increasingly self-conscious about my status as a “resident alien.” While I had plenty of opportunity to speak to Americans, I could not speak as an American. And that is why the election of a dangerous demagogue to the presidency of the United States made me more, not less, determined to take on citizenship. Now more than ever I want to be a fully paid-up member of this society — and fight for the survival of liberal democracy alongside my new compatriots.

The oath of citizenship moved me more than I had expected. For a moment, I choked up and found it difficult to get the words out. But then my voice took on a new resolve: proud and determined, I swore to “defend the Constitution and the laws of the United States of America against all enemies, foreign and domestic.”