There was a new tone in President Biden’s speech on the anniversary of the Jan. 6 riot in which a violent mob of Trump supporters sought to overturn the results of a legitimate presidential election. More forcefully than he had before, the current president took to task the man he had defeated for inciting cultlike followers to trash the U.S. Capitol, with deadly consequences.

Donald Trump and those he stoked with his “web of lies” that the 2020 election was stolen from him “held a dagger at the throat of America — at American democracy,” Biden said. His 25-minute address was the muscular pushback that so many Democrats have been waiting to hear from Biden, who has generally — and wisely, in my view — preferred to ignore the predecessor he refers to as “the former guy."

What really preoccupies the president, however, was summed up in a quieter passage that came near the end of the speech, one that didn’t get as much notice. If there is a sweeping premise that defines what Biden views as the greatest challenge of his presidency, it is that the United States must disprove a growing cynicism about democracy itself — not just in this country, but around the world. Amid deep political polarization and an undermining of norms, the processes have become so messy and fraught that people are losing faith that democratic systems are still capable of functioning and of delivering results.

“Look, folks, now it’s up to all of us — to ‘We the People’ — to stand for the rule of law, to preserve the flame of democracy, to keep the promise of America alive. That promise is at risk, targeted by the forces that value brute strength over the sanctity of democracy, fear over hope, personal gain over public good. Make no mistake about it: We’re living at an inflection point in history,” Biden said.

“Both at home and abroad, we’re engaged anew in a struggle between democracy and autocracy, between the aspirations of the many and the greed of the few, between the people’s right of self-determination and the self-seeking autocrat,” he continued. “From China to Russia and beyond, they’re betting that democracy’s days are numbered. They’ve actually told me democracy is too slow, too bogged down by division to succeed in today’s rapidly changing, complicated world. And they’re betting — they’re betting America will become more like them and less like us.”

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This fear that democracy is eroding, leaving a vacuum to be filled by authoritarianism, took root with Biden well before the siege of the Capitol. When he was running for president, he often spoke of a book, published in 2018, that had left a deep impression on him — “How Democracies Die,” by Harvard government professors Steven Levitsky and Daniel Ziblatt.

The president returns to the subject often, not just in the context of the assaults on democratic norms and institutions that escalated during the Trump era but also as he argues for the passage of his ambitious domestic agenda. Last June, for instance, when bipartisan negotiators reached agreement on a framework for a roughly $1 trillion infrastructure package, he declared that it was about far more than roads and bridges and faster broadband: “This agreement signals to the world that we can function, deliver and do significant things. ... It also signals to ourselves and to the world that American democracy can deliver.”

He made much the same point in December as he opened a virtual gathering of representatives of more than 100 countries that the White House billed as a “Summit for Democracy.” Biden warned of “dissatisfaction of people all around the world with democratic governments that they feel are failing to deliver for their needs. In my view, this is the defining challenge of our time.”

It is also the defining challenge of the Biden presidency. Though Trump accelerated the crumbling of the guardrails that have protected democratic institutions — and so opened the way to the Jan. 6 attack — the problem did not begin with him. And while the system was strong enough to hold, the forces that have undermined it have not subsided. In marking the horrors of that day a year ago, Biden was right to remind us to keep our gaze high and our faces turned forward. The rest of the world is looking to this country as a test of whether democracy is worth salvaging.