The bus formerly known as “No Malarkey” was rolling east through the darkness along Iowa’s Route 20 when Joe Biden got the call. Tony Blinken, a senior foreign policy adviser stretching back to Biden’s days in the U.S. Senate, was on the phone to deliver stunning news: A drone strike in Baghdad had just killed Qasem Soleimani, a top Iranian general and the powerful architect of decades of lethal attacks in the Middle East. In all probability Soleimani’s death had been the work of American special operations forces. Biden was heading to a presidential campaign event in Dubuque. But as he hung up with Blinken, he must have felt as if he were traveling back in time, to October 2002, when then senator Biden voted in favor of allowing then president George W. Bush to invade Iraq.

Certainly Bernie Sanders has wasted no time in trying to drag his current Democratic primary rival back to those controversial days. Sanders, who in 2002 was Vermont’s sole congressman, delivered an impassioned speech against authorizing Bush to use force against Saddam Hussein and then voted no. The ruinous Iraq war that followed—and in some ways continues to unfold—made a strong case that Sanders was right. In 2016, he used Hillary Clinton’s vote in favor of the Iraq war to help mount a surprisingly strong primary bid. Now the killing of Soleimani, and the prospect of widening military action against Iran, have given Sanders an opening, one month before the Iowa caucuses, to hammer at a pillar of Biden’s 2020 rationale: that the former vice president’s vaunted record of experience is in fact malarkey because Biden has too often made the wrong call on big issues.

“We’re in this moment on Iraq where that fundamental flaw—I don’t want to get too soft here—that fundamental error in judgment by Joe Biden and many other establishment politicians has continued to remind people of what a disastrous mistake that 2002 vote was,” Faiz Shakir, Sanders’s campaign manager, told me shortly after the Soleimani news broke. “Bernie Sanders has a proven record of fighting for the right thing at the right time—on the first instance, not on the second, third, fourth, or fifth try, as the case might be with Joe Biden. So yes, you’re going to hear a lot more about his Iraq vote from us.”

Foreign policy is usually a tough sell in primary contests. President Donald Trump and Ayatollah Ali Khamenei will determine if it becomes a higher priority over the next few weeks. Then the question will be whether centrist voters are drawn even tighter to Biden as a generally reassuring presence in a looming crisis, or whether they’re outnumbered by leftish voters on guard for any appeasement of Trump. “The debate around Trump needing authorization to conduct further tit-for-tat with Iran could become a fault line in the primary,” said Brian Fallon, who was a top strategist for Clinton in 2016. “On the left, even insisting on congressional authorization is going to be viewed as, It’s okay to go to war with Iran, you just want Trump to do it the right way. Similar to when people were pussyfooting around on impeachment. Anything less than full-throated opposition to escalation with Iran will be seen as going down the same path as in 2002, and mark you as being part of the Democratic old guard.”

The Biden camp continues to sound confident, with public polling and fundraising numbers rising just as the first actual votes are finally within sight. “After a period of trying on other candidates for size, we’re seeing voters who are coming home to Biden here in the final crunch because the stakes in the election are so high,” a top Biden adviser told me. “Donald Trump has spent the duration of this race attacking Biden viciously, attacking his family, getting himself impeached over it. And it has not hurt Biden. Biden is still winning. Voters look at that and say, Here’s somebody who has withstood the full brunt of Donald Trump’s attacks for 10 months and has emerged stronger for it. That’s the kind of nominee that Democrats are hoping to put forward to run against Trump.”