Ronald A. Klain served as a senior White House aide to both Presidents Barack Obama and Bill Clinton and was a senior adviser to Hillary Clinton’s 2016 campaign.

As Democrats engage in soul-searching about their future, here’s an idea: Progressives should claim one of the oldest ideas in American thought — the concept of American exceptionalism — for their own.

American exceptionalism, the view that the United States’ revolutionary founding, devotion to liberty and natural resources make it a country with a unique role in the world, has traditionally been the province of conservatives, who have tended to add a religious dimension to the mix. Ronald Reagan’s invocation of the “shining city upon a hill” exemplified this conservative embrace.

Liberals have more often shied away from such rhetoric. When President Barack Obama was asked about exceptionalism at a 2009 news conference, he replied dismissively, “I believe in American exceptionalism, just as I suspect that the Brits believe in British exceptionalism and the Greeks believe in Greek exceptionalism.”

Then, in one of the least-appreciated intellectual dimensions of his presidency, Obama redefined the exceptionalist idea during his second term and set forth a new vision of exceptionalism based — not on America’s founding or divine designation — but on the extraordinary acts that Americans perform to help others in need, not just in the United States, but throughout the world.

I witnessed this evolution as White House Ebola response coordinator, when Obama offered a compelling articulation of this concept of American exceptionalism after an emotional meeting with health-care workers who had been battling Ebola in West Africa. He described an America “defined by courage and passion and hope and selflessness and sacrifice and a willingness to take on challenges” that other nations cannot, or will not, tackle. “This is America,” Obama said. “We do things differently.”

Obama’s vision of an American exceptionalism fostered by each generation’s sacrifice at home and abroad is idealistic and progressive. Whether it is peacekeepers ending slaughter in the Balkans, Peace Corps workers toiling away in a remote village in South America, a SEAL team rescuing hostages in the Middle East, or a church group welcoming a refugee family into a small town in Ohio, this concept of American exceptionalism was captured well by Hillary Clinton’s 2016 phrase, “America is great because America is good.”

As Obama took his journey toward an embrace of a new American exceptionalism, Donald Trump was tugging the Republican Party in the opposite direction, away from its historical devotion to the exceptionalist ideal. In 2013, before his presidential campaign, Trump joined Russian President Vladimir Putin in criticizing Obama’s call for a more interventionist approach to the crisis in Syria. Obama, citing the need for humanitarian intervention, argued, “That’s what makes America different. That’s what makes us exceptional.” Trump took offense, asserting that Obama’s attitude that the United States is exceptional “is very insulting” to other countries.

Now, the core idea of Trump’s America First, “Art of the Deal” presidency — that America should look out only for America and should not take on any risk, sacrifice or concession not in its immediate self-interest — represents a fundamental rejection of exceptionalism. It explains why Trump’s reaction to criticism of Putin’s murderous regime was not to deny Putin’s wrongdoing but to posit moral equivalency between the United States and Russia: “You think our country’s so innocent?” So much for America as that city on the hill.

(Bastien Inzaurralde/The Washington Post)

And of course, this rejection of an exceptional role for the United States in the world undergirds Trump’s views on refugees. It is why Trump called the Obama administration’s agreement to resettle 1,200 refugees from a remote island near Australia the “worst deal ever.” Trump cannot imagine the United States undertaking the resettlement because it is compassionate or offers a unique beacon of hope to people seeking freedom; for him, this is a deal for suckers and should be rejected.

But he is wrong, and Obama was right: The United States is better than this. That is why now is the time for the left to throw off its historical skepticism of, even antagonism toward, American exceptionalism and unabashedly challenge Trump with a progressive formulation of this ideal.

“The Resistance” is writing a new chapter of grass-roots activism. That protest has so far been mostly defined by what it is against: Trump’s executive orders, repeal of Obamacare, the intolerance spewed by the alt-right. But the people filling the streets are not merely opposed to Trump: Most are drawn to the idea of standing for something larger than themselves. Embracing a progressive concept of American exceptionalism — of a national mission and determination to, as Obama said, build a “better world not just for ourselves but for people in every corner of the Earth,” as only the United States can — would add a noble and affirmative message to the new movement, and accelerate its development into something more than a left-leaning version of the tea party’s nihilism.

Democrats are struggling to get past the blame game over 2016 and their divisive party chair election. If they want to harness the energy of the streets, demonstrate that they are a party of principle and ideas, and create a home for today’s idealistic young activists, they should step into the void created by Trumpism, turn the tables on decades of positioning in American politics and become the party of American exceptionalism.