Cedar Falls, Iowa—A roar of approval filled the packed ballroom on the University of Northern Iowa campus when Black Hawk County Supervisor Chris Schwartz reminded hundreds of Iowans that, almost two decades ago, “It was Bernie Sanders who stood up to George Bush and said no to war!”

The applause was just as loud a few minutes later, when Congressional Progressive Caucus cochair Mark Pocan, from neighboring Wisconsin, told the Iowans he was barnstorming for Sanders because “Yes! We must stop endless wars!”

The national media has moved on from discussing the prospect that President Trump’s decision to kill a key Iranian general had brought the Middle East to “the brink of war.” But concerns about issues of war and peace—which briefly upended the national debate in early January—continue to influence the race for the Democratic presidential nomination. That’s benefiting Sanders, especially in Iowa.

There’s little question that the senator from Vermont is surging in the state that will hold the first caucuses of the 2020 cycle on February 3. A fresh New York Times/Siena College Poll positions Sanders in a clear front-place position in the state, with 25 percent support, versus 18 percent for former South Bend, Indiana, mayor Pete Buttigieg, 17 percent for former vice president Joe Biden, and 15 percent for Massachusetts Senator Elizabeth Warren. A new Emerson College poll has Sanders opening up an even wider lead. Both polls, along with a number of other recent surveys, suggest the senator has gained a good deal of ground since the release of the highly regarded Des Moines Register/CNN poll in early January, which gave Sanders a narrow lead over the rest of the field.

You’ll hear plenty of speculation about why Sanders is rising at the point when it matters most. But not enough attention has been paid by pundits at the national level to the resonance of the anti-war message that Sanders delivered in the first weeks of 2020. After President Trump ordered the killing of Iranian Maj. Gen. Qassim Suleimani, when many Americans feared the country was careering toward another Middle East war, Sanders delivered an immediate and aggressive anti-war message. Recalling his opposition to past wars, Sanders declared, “I was right about Vietnam. I was right about Iraq. I will do everything in my power to prevent a war with Iran. I apologize to no one.”

He kept reinforcing that message in Iowa, New Hampshire, and other states, where he incorporated a more detailed critique of “endless wars” into his stump speech—to such an extent that The Atlantic noted, “Bernie Sanders Has Something New to Talk About: The Iran crisis is giving him a chance to differentiate himself—just in time for the Iowa caucuses.” He did the same in Washington, where he and Representative Ro Khanna sponsored the No War Against Iran Act.

“I firmly believe the reason Bernie has shot to the lead has everything to do with Iran. He was decisive on this. We co-introduced legislation the day after the strike to stop funding for the war. And then went across Iowa hitting the anti-war message,” says Khanna. “Sanders hammered the anti-war message for weeks. He had the great line he started using: Instead of spending 1.8 trillion on military budgets, why don’t we use some of those resources to tackle climate change. People tuned in that he had blasted the defense budget.”

Khanna, who has emerged as a leading anti-war voice in the Congress and nationally, campaigned for Sanders in Iowa in early January. He says Democrats and independents made a point of saying how important it was to them that Sanders was delivering a strong rebuke to endless wars. “It’s just shocking to me that what’s so obvious to explain Bernie rise is being missed by the media,” says Khanna. “Of course for Bernie, taking that anti-war position was just pure principle. It was so instinctive for him that we needed to issue a statement opposing the assassination and re introducing legislation to block the funding. He didn’t need a committee. His bold action stemmed from a lifetime of commitment to these issues. And Iowa voters saw this.”

That’s not an uncommon assessment. “His anti-war position is important to a lot of people. It’s important to me,” said Whitman Cler, a student who was volunteering for Sanders at the University of Northern Iowa event on Saturday.

Schwartz, who serves as Iowa state director of Americans for Democratic Action in addition to his work as a local elected official, argues, “This country is sick of endless wars, and I think that’s especially true in Iowa. So, yes, of course people are noticing that Bernie is talking about this. Iowa has always had an anti-war streak. There’s a long history of peace activism—of voting for anti-war candidates.”

The state’s caucuses gave a significant boost to George McGovern’s anti-war bid in 1972, and to a number of other anti-war candidates along the way. Perhaps most famously, Iowa was the place where Barack Obama gained traction as a Democratic contender in 2007 and 2008 by emphasizing the fact that he had spoken out against going to war with Iraq in 2002—when other leading Democrats had backed the war.

Schwartz says he caucused for Obama in 2008 because the candidate had opposed the rush to war. And it is one of the reasons he will caucus for Sanders this year. “Sanders has credibility as an anti-war candidate. He opposed the Iraq War,” says Schwartz. “People know that, and it matters to them, just as it matters that he is now speaking out against war with Iran.”

Ro Khanna thinks that’s the key. “Anti-war is not just good substance,” he says. “It’s winning politics.”