Joe Biden.

The most important element of Joe Biden’s foreign-policy speech last week lay not in the details (which were thin) but in his embrace of one critical idea. “The overarching purpose of our foreign policy,” he said at City University of New York, must be to “defend and advance our security, prosperity, and democratic values that the United States stands for.”

President Donald Trump’s “failures to uphold basic democratic principles have muddied our reputation and our place in the world, and ... our ability to lead the world,” Biden added. In other words, the greatest soft power America possesses – its post World War II status as the world’s premier democracy – is being squandered, both at home and in Trump’s interactions with allies and adversaries. Whether or not you support Biden, I believe he has advanced the most critical foreign-policy issue of 2020: the urgent need to restore democratic norms at home and revive US leadership of the “free world” abroad.

Let me be more specific. America’s premier standing in the world over the last seven decades has relied heavily on admiration and respect for the success and functionality of its system and institutions, including from citizens and leaders of adversarial nations. It has always astonished me how many leaders of dictatorial regimes send their children to study here. China was already sending tens of thousands as far back as the 1980s.

So, when democratic norms are shredded within the USA, and vicious partisanship hobbles the US Congress, the rest of the world takes keen notice. When President Trump gives a green light to racists, in Charlottesville, Va., and elsewhere, and cages asylum-seeking children at the border, they are startled. Over and over I have heard, in Europe, the Mideast, and Asia over the last couple of years, the same question: “What has happened to your country?”

And when Trump began encouraging violence toward the mainstream media and denouncing journalists as “enemies of the people,” my Russian journalist colleagues were astonished and dismayed at first. Now they take Trump rhetoric for granted and make clear that they assume U.S. democracy is on the way down, just as Vladimir Putin says bluntly in public. That, they say, is the reason it’s so easy for the Kremlin to meddle.

So Trump’s disdain for checks and balances and traditional democratic norms has sullied America’s global reputation and the respect that adversaries pay. Even more disturbing, Trump’s disdain for democratic allies comes at a particularly dangerous moment in history, when global change is happening with incredible speed and intensity.

“Nations are more intertwined than they ever have been,” Biden rightly said. The threats from climate change, nuclear proliferation, cyber warfare, and mass migration require the US to lead the world’s democracies on these issues, which would then increase the pressure on autocracies to behave better. Yet, “Donald Trump’s brand of America First has too often led to America alone, making it much harder to mobilize others,” said Biden. That has been true on every issue cited above.

Moreover, at this time of epochal global shifts, the idea and practice of democracy is under more pressure than at any point in our lifetimes. China and Russia are openly promoting their authoritarian ideologies as an alternative to liberal democracy, which they claim is a failure. Extreme populist nationalism and xenophobia are on the rise around the globe, including, of course, in the US. However, at least Biden understands the criticality of making “democracy once again the watchword of US foreign policy, not to launch some moral crusade (meaning no more efforts to impose democracy) but because it’s in our enlightened self-interest.”

“The United States must lead not just with the example of power, but the power of our example,” he added. This is the message any Democratic candidate must promote.