While waiting for Biden that evening in Des Moines, one of the pre-program speakers led the crowd in singing “God Bless America.” When he arrived, Biden the candidate still winked and shot finger guns at well-wishers and hugged them afterwards, but it was Biden the commander-in-chief that his advisers wanted on display. The former veep pilloried what he viewed as Trump’s recklessness and called for congressional authorization of any further military engagement with Iran. His aides began planning a major speech on the issue in New York for the following Tuesday.

To Biden’s aides, it was their man’s chance to seize the moment.

“The more the world seems in disarray, especially with Trump as an erratic accelerant to that disarray, the more people seem to be looking for some return to normalcy and strong and steady leadership as opposed to erratic leadership,” said a Biden adviser. “There's now an even greater premium on experience and being ready on Day One to deal with the mess Trump leaves. To state the obvious, that plays to Biden’s strengths.”

But it also plays to some of his weaknesses. A young voter stood up and asked Biden “How could we trust your judgment?” After all, the voter said, he’d gotten two of the biggest questions in recent years wrong: the 2002 Iraq War vote when he was a senator and the 2011 Navy SEAL raid on Osama bin Laden’s hideout in Abbottabad, Pakistan, which Biden, then vice president, counseled Obama against.

Biden was a senator for 36 years and vice president for eight. His response was essentially that the questioner was cherry-picking two decisions and ignoring everything else in his record. What about his role in bringing down Slobodan Milosevic or his advice—ignored by Obama—not to surge troops into Afghanistan in 2009 or his rallying NATO to confront Russia over Ukraine?

On Iraq, Biden gave a familiar answer that Democratic senators who voted for the invasion have been making for 17 years: It was a vote to give President George W. Bush leverage at the United Nations to bolster a weapons inspection regime, not to greenlight an imminent attack. (This is historically accurate, but a bit like arguing you let a college-aged friend borrow your credit card only for buying books for his fraternity and then being surprised about all the pot and booze he added to the bill.)

On the bin Laden raid, Biden, changing his story a bit, insisted that after a larger meeting at which he expressed reservations, he privately told Obama to go for it. (During his lengthy response, at one point, Biden accidentally said Saddam Hussein when he meant Osama bin Laden.)

Despite the tough question, Biden seemed pleased. If the subject is foreign policy, Biden believes he’s winning. He’d rather talk for hours defending his worst foreign policy blunders than spend a minute focusing on, say, busing or bankruptcy reform. “It’s not to suggest I didn’t make mistakes in my career,” he told the young questioner in Des Moines. “But I will put my record against anyone in public life in terms of foreign policy.”

Bernie Sanders was the only rival who seemed to welcome that challenge. While Biden’s strategy is that of a traditional primary frontrunner—ignore your primary opponents and focus on your general election opponent—Sanders has the classic strategy for the person in the No. 2 spot: argue it’s a two-person race.

In Iowa last weekend, where there were dozens of candidate events, Sanders was the only other politician who seemed to relish discussing the confrontation with Iran—and how the Iraq war and the Democrats who supported it helped bring about the current situation.

“What Iran has done is really highlighted both Bernie Sanders and Joe Biden as representatives of two different poles in the Democratic party: one a much more hawkish interventionist arm of the party, which used to be dominant, and then Bernie Sanders, representing a more diplomacy-oriented approach, a more collaborative international approach that is ascendant in the party,” said Jeff Weaver, one of Sanders’s top advisers, who went on to ding Biden for the 2002 Iraq vote.

The common assumption about Democratic base politics has been that the domestic trumps the international, that voters in Dubuque would rather hear about how candidates are going to fix their healthcare than about how they’re going to fix the Middle East.

But that’s not entirely true. Every open Democratic primary since 9/11 has been about war, and the beneficiary of the debate over that issue hasn’t been easy to predict. In 2004, another insurgent Vermonter -- Howard Dean -- based his entire candidacy on his opposition to Bush’s invasion of Iraq, which was enormously unpopular among Democrats and which John Kerry had voted to authorize. Kerry, after struggling in 2003, when Dean’s antiwar message thrilled liberals and filled stadiums, easily defeated his New England rival when voting began in 2004.

In 2008, Barack Obama’s opposition to the Iraq War was perhaps the single most important argument he made to show voters that, according to the two buzzwords of the primary, his “judgment” was superior to Hillary Clinton’s “experience.” By then, voters had grown tired of the body bags coming home from Baghdad and Kandahar, and the politics of the wars had ricocheted against the Republican Party and hawks like John McCain. But Obama soon made it clear that voting to invade Iraq didn’t disqualify Democrats from governing. He chose Biden, who, like Clinton, voted to authorize the war, as his running mate and made Clinton his secretary of state. In the 2016 Democratic primaries, Sanders was unable to run the same play against Clinton. He frequently highlighted her Iraq vote to no avail.

This election, 2020, seemed like it might be different. But Iran has belatedly forced a serious foreign-policy debate among the major Democratic candidates, with Sanders and Biden representing opposite sides of a basic question that could define the next administration: What do Democrats believe about America’s role in the world? And do they have a national-security message that can defeat Trump’s chest-thumping bravado?

***

Earlier on the same day Biden spoke, Sanders stumped in Grundy Center, about 90 minutes northeast of Des Moines. It was a small working class audience and Sanders, after blasting Biden on Iran for the cameras, returned to health care.

Though the term is not often used nowadays, the Sanders town hall format is what sixties-era activists used to call “consciousness raising.” He prods ordinary people to stand up and describe for their fellow citizens the depravities they’ve experienced in the American healthcare system. Older radicals used the method to make working people aware that they were oppressed, that they weren’t the only ones, and that they could do something about it.

These sessions usually surface so many sad stories that Sanders has a regular joke about how his wife Jane complains that his events are too depressing. He then points to an aide who will be handing out Prozac on the way out.

The Sanders view is that, quite literally, this is how the revolution starts. Raise enough consciousness among regular people about the vagaries of the health insurance industry and eventually people will be organizing together and clamoring to trade in their own insurance plans in favor of Medicare for All. This is not just how Sanders sees healthcare, but it’s how he sees almost every issue, including foreign policy.

“I was mayor of the city of Burlington, Vermont, in the 1980s, when the Soviet Union was our enemy,” he said in a 2017 address at Westminster College, in Missouri. “We established a sister city program with the Russian city of Yaroslavl, a program which still exists today. I will never forget seeing Russian boys and girls visiting Vermont, getting to know American kids, and becoming good friends. Hatred and wars are often based on fear and ignorance. The way to defeat this ignorance and diminish this fear is through meeting with others and understanding the way they see the world. Good foreign policy means building people-to-people relationships.”

But how that commendable insight translates into policy has been a struggle for Sanders to articulate.

Sanders’s foreign-policy views were first shaped by his left-wing activism during the Cold War, when the animating force on the far left was opposition to American adventurism in the name of anti-communism. As the mayor of Vermont’s largest city—a small town of 40,00, really—Sanders actually had a foreign policy. He visited Cuba, he became involved in Latin American politics centered on opposition to anything that smacked of U.S. imperialism, and he and Jane even honeymooned in the Soviet Union in 1988. (This litany of activities is frequently raised by Sanders’ rivals as deeply problematic for a general election against Trump.)

But when he got to Congress in 1991, Sanders spent the next few decades, first as a member of the House and then as a senator, strangely uninterested in foreign policy. When he ran for president in 2016, the old image of Sanders from his mayoral days as a pro-Sandinista Chomskyite is what stuck.

His 2017 speech was meant to address that. For years now, progressives have been debating how to articulate an American foreign policy that rejects what they see as the militarism of liberal internationalists, who make up the Democratic Party establishment, and left-wingers who reject any use of American power in the world as inherently tainted. Arguably, that was something Obama managed to achieve, but many on the left viewed him as just another militarist by the time he left office.

Sanders still peppers his foreign-policy remarks with a long recitation of America’s anti-democratic history, especially in Latin America and the Middle East, during the Cold War, and the worst mistakes of the post-9/11 era. But over time he has gradually shifted from an emphasis on how America has messed up the world in the past to how to confront looming threats to international democracy today.

He has repeatedly praised America’s role in creating the United Nations and expressed deep admiration for the Marshall Plan, which helped rebuild Germany and western Europe after World War II. In 2018, he identified growing authoritarianism as one of the great foreign policy challenges for the United States. It was a turning point for Sanders: The villains in that speech are not Americans meddling in Chile or invading Iraq, but the “the authoritarian axis”—a phrase that echoed Bush’s “axis of evil”—and in Sanders’s telling includes countries like Russia, Saudi Arabia, the Philippines, Turkey and Brazil, where there are “movements led by demagogues who exploit people’s fears, prejudices and grievances to gain and hold on to power” and are also handmaidens to billionaires and oligarchs, more familiar Sanders bogeymen.

While he called for a movement to “combat the forces of global oligarchy and authoritarianism,” the details of how a Sanders administration would use American power to do that have been vague. He had identified what he believed was the threat of our time but he didn’t say how America could counter it.

Meanwhile, Biden, along with most foreign policy centrists in the Democratic Party, has also shifted. As he pointed out in Iowa, Biden was a forceful internal opponent of the Obama surge in Afghanistan. He was deeply skeptical of the Libya intervention, which Obama came to regret, and Biden has recently called for removing most troops from Iraq and Afghanistan. Biden and his ideological kin have recognized that there is almost no constituency left in the Democratic Party for the kind of hawks that dominated in the nineties and early 2000s.

But on the question of American leadership and whether American power can be virtuous, Biden is unequivocal. His campaign is premised on the idea that a President Biden can quickly restore America’s role as a force for good. For progressives that is not comforting. They fear that Biden and his advisers could easily revert to the hawkishness that dominated recent history.

In talking to Democratic foreign policy advisers across the spectrum, I heard people in Biden’s orbit caricature Sanders as a Corbyn-like old leftist who never outgrew his radical roots. And I heard Sanders’ allies describe Biden as a bloodthirsty neoliberal warmonger who will return to militarism once elected. The truth is that Democratic voters have forced both men to shift: Sanders to accept that if he wants to be president he needs to be comfortable with taking the reins of a superpower and Biden with the fact that the legacy of the Iraq War has poisoned the idea of liberal interventionism to an entire generation. (Elizabeth Warren and Pete Buttigieg fit neatly on this continuum, with Warren closer to Sanders and Buttigieg closer to Biden.)

All three—Sanders, Warren and Buttigieg—have tried to articulate an alternative vision to a Biden-style establishment Democratic foreign policy--what Sanders’ advisers call the D.C. “blob.”

And there are notable differences on some key issues. Sanders and Warren are willing to leverage aid to Israel to change the country’s behavior toward the Palestinians, while Biden isn’t. Sanders opposes the recent USMCA trade deal, while Warren and Biden support it. Sanders and Warren would leave almost no footprint behind in Iraq and Afghanistan, while Buttigieg and Biden want some forces to respond to any resurgence of al Qaeda and ISIS.

Progressives have also changed the politics of foreign policy. Democrats across the spectrum no longer believe that a reflexive toughness to international crises is a prerequisite for victory. In 2004 Kerry, who in his youth was most famous for his opposition to the Vietnam war, reinvented himself as a war fighter for the general election. (He lost.)

In 2020 the pressure for Democrats in their response to the killing of Soleimani was to show they would not exaggerate or dwell on his crimes in the Middle East and that they would not say anything that would encourage escalation with Iran. Warren originally tweeted that “Soleimani was a murderer, responsible for the deaths of thousands, including hundreds of Americans.” The next day, in a tweet that focused solely on Trump, she wrote that the president had “assassinated a senior foreign military official.” Gone was any description of Soleimani’s history in the region.

But in the end, the 2020 foreign policy debate among Democrats is likely to play out a lot like the 2020 domestic policy debate among Democrats: with the establishment candidate co-opting just enough of the left’s grievances to snuff out the challenge.

The Sanders wing long ago won the debate about deemphasizing the use of force, ending “forever wars,” prioritizing diplomacy, and bolstering relationships with democracies. But what the progressives have not yet been able to fully articulate—and there’s a vast literature that has tried—is how a President Sanders or Warren or even Buttigieg, who have all identified promoting democracy and curtailing the rise of authoritarianism as major modern priorities, would actually do that.

I asked a top adviser to Sanders about whether there are more details to add to Sanders’ 2018 call to reverse the rising tide of autocrats.

“We’re working on it,” he said.