In months of debates, interviews and campaign appearances in the 2016 primary, Sen. Bernie Sanders (I-Vt.) was unable to take down Hillary Clinton by attacking her vote for the Iraq War. Clinton was clearly the more hawkish of the two contenders, defending President Barack Obama’s handling of the war against the Islamic State and calling for a responsible drawdown in Afghanistan. Despite the Democratic Party’s staunch opposition to the war, Clinton won the nomination. She acknowledged the vote was a mistake, but also truthfully recounted that she understood President George W. Bush to be using the resolution to get the United Nations to buy into a joint resolution.

In 2020, Sanders is now making the same argument against former vice president Joe Biden, namely that his Iraq War vote is disqualifying. As Clinton did, Biden may point to his overall record on foreign policy under Obama (e.g., opposing the surge in Afghanistan or using sanctions and diplomacy to get the Iran nuclear deal). He also may attack Sanders as vulnerable — that is to say “unelectable” — because President Trump will easily tag him as weak on national security.

Alternatively, Biden may try to parse out his Iraq War vote. As Clinton said she did, Biden thought at the time the resolution for use of force was a way of pressuring the United Nations to get on board — in other words, to beef up a diplomatic effort with the threat of force behind it. The Post’s fact-checker recounts that by 2005, Biden confessed on “Meet the Press”: “‘It was a mistake to assume the president would use the authority we gave him properly.’ He repeated his previous criticism of Bush’s tactics: ‘We went too soon. We went without sufficient force. And we went without a plan.’” (Biden recently got in hot water for claiming he “immediately” opposed the war. As The Post’s fact-checker reported: “Biden was critical of how the war was managed and the reasons it was waged, and thus he would be on more solid ground if he simply called himself a war critic.”)

In any case, Sanders’s critique might get him only so far, even with progressive voters. Biden plainly is skeptical of Trump’s rush to war now and fought in the Obama administration to stop further troop commitments. At worst (from the perspective of the average Democratic primary voter), one could say he was too trusting of Bush, became a war critic (although not immediately), showed his commitment to thoughtful internationalism under Obama and now seems fully capable of taking down Trump on his foreign policy blunders.

Voters are remarkably willing to judge candidates on what they are saying now as long as the candidate appears trustworthy and confident. Many candidates, to the frustration of opponents and/or media critics, have gotten away with changes in position or with past missteps. Voters tend to look at candidates in the present, assess their sincerity and demeanor, and then decide if they can trust them to do the right thing when the candidate is the decision-maker.

In short, it is not clear that Sanders will have any more luck taking down Biden on Iraq than he had taking down Clinton. Four years later, the issue may been even less potent than it once was. The greater challenge to Biden may come from former Navy intelligence officer and former South Bend, Ind., mayor Pete Buttigieg, who was too young to vote on the Iraq War, now comes across authoritative on national security and has the added benefit of being able to scold Trump for using a “bone spur” deferment to get out of the Vietnam War. One suspects foreign policy will be front and center in the debate next week, even if it is not the decisive issue for most voters.

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