Joe Biden has an issue that hasn’t played out yet in this election: his role in the launch of the Iraq war.

The Iraq war has been a prominent, even decisive issue, in some recent US presidential elections. It played a significant role in the surprise presidential primary victory won by a freshman senator from Illinois named Barack Obama in 2008. His heavily favored Democratic primary opponent, Hillary Clinton, had voted in the US Senate to authorize the war, and Obama didn’t let her forget it during that contest.

In 2016, Donald Trump invoked the Iraq war against opponents in his own surprise victory in the Republican primary. And then he used it against Clinton, most likely with significant effect, in the general election that followed.

Biden did vastly more than just vote for the war. Yet his role in bringing about that war remains mostly unknown or misunderstood by the public. When the war was debated and then authorized by the US Congress in 2002, Democrats controlled the Senate and Biden was chair of the Senate committee on foreign relations. Biden himself had enormous influence as chair and argued strongly in favor of the 2002 resolution granting President Bush the authority to invade Iraq.

“I do not believe this is a rush to war,” Biden said a few days before the vote. “I believe it is a march to peace and security. I believe that failure to overwhelmingly support this resolution is likely to enhance the prospects that war will occur …”

But he had a power much greater than his own words. He was able to choose all 18 witnesses in the main Senate hearings on Iraq. And he mainly chose people who supported a pro-war position. They argued in favor of “regime change as the stated US policy” and warned of “a nuclear-armed Saddam sometime in this decade”. That Iraqis would “welcome the United States as liberators” And that Iraq “permits known al-Qaida members to live and move freely about in Iraq” and that “they are being supported”.

The lies about al-Qaida were perhaps the most transparently obvious of the falsehoods created to justify the Iraq war. As anyone familiar with the subject matter could testify, Saddam Hussein ran a secular government and had a hatred, which was mutual, for religious extremists like al-Qaida. But Biden did not choose from among the many expert witnesses who would have explained that to the Senate, and to the media.

Biden’s selling points as a candidate often lead with his reputation for foreign policy experience and knowledge. But Iraq in 2002 was devastated by economic sanctions, had no weapons of mass destruction, and was known by even the most pro-war experts to have no missiles that could come close to the United States. The idea that this country on the other side of the world posed a security threat to America was more than far-fetched. The idea that the US could simply invade, topple the government, and take over the country without provoking enormous violence was also implausible. It’s not clear how anyone with foreign policy experience and expertise could have believed these ideas.

Senator Dick Durbin, who sat on the Senate intelligence committee at the time, was astounded by the difference between what he was hearing there and what was being fed to the public. “The American people were deceived into this war,” he said.

Regardless of Biden’s intentions – which I make no claim to know or understand – the resolution granting President Bush the authority to start that war, which Biden pushed through the Senate, was a major part of that deception. So, too, was the restricted testimony that Biden allowed. The resolution itself contained deceptive language about a number of pretexts for the war, including al-Qaida and weapons of mass destruction that Iraq did not have.

The Iraq war has generally been seen as one of the worst US foreign policy blunders in decades. It fueled the spread of terrorism and destabilized the Middle East and parts of north Africa. “Isil is a direct outgrowth of al-Qaida in Iraq, that grew out of our invasion,” noted President Obama.

More than 4,500 US soldiers, and nearly as many US military contractors, lost their lives; tens of thousands were wounded, with hundreds of thousands more suffering from post-traumatic stress disorder. Estimates of Iraqi deaths run as high as 1 million.

At the very least, Biden should explain why he played such a major role in winning the authorization from Congress for President Bush to wage this disastrous war.