I don’t know if the moderators of tonight’s Democratic primary debate are taking requests, but here’s my question for former vice-president—and current frontrunner—Joe Biden:

“Mr. Biden, the last time you were running for president, you promised that if George W. Bush ‘takes this nation to war in Iran, without congressional approval, I will make it my business to impeach him.’ Now, over a decade later, war with Iran is again on the horizon, and just this Monday, the president said he does not need congressional authorization to wage war. If he acts on that belief, will you call for Congress to impeach President Trump?” 

In December 2007, when then-Senator Biden made those remarks, the crowd in Davenport Iowa answered with hearty cheers.

At the time, there was a serious concern that President Bush would use prior congressional authorizations–like the 2002 Iraq War resolution or the post‑9/​11 Authorization for the Use of Military Force (2001 AUMF)–as cover for a new war with Iran. A month before Biden’s speech, then-Senator Barack Obama introduced a joint resolution designed to foreclose that option. “There is absolutely no reason to trust that this Administration will not use existing congressional authorization to justify military action against Iran,” Obama warned.

Here we are again: now, nearly 12 years later, there’s no reason to trust that this administration won’t use the 2001 AUMF as justification for war with Iran. Secretary of State Mike Pompeo has suggested as much, behind closed doors, to members of the House Armed Services Committee. 

Joe Biden knows something about the 2001 AUMF: he voted for it, three days after 9/11. And, like practically every other member who passed that resolution, he described it as a limited measure, aimed at those who were responsible for the attacks. As the New York Times reported after the vote: “Senator Joseph R. Biden Jr., chairman of the Foreign Relations Committee, said Congress was not ceding its constitutional authority to declare war or intending to write a measure like the Gulf of Tonkin resolution, which President Lyndon B. Johnson used in 1964 to justify escalation of the war in Vietnam.” 

The 2001 AUMF has now been in effect almost three times as long as the Gulf of Tonkin Resolution, and the current administration thinks it can draw on that authority to wage war over the “Gulf of Oman incident.” 

In the short term, Congress has limited means available to it for heading off war. Most of the measures currently being debated on the Hill would have to make it past a presidential veto. A sense-of-Congress resolution threatening impeachment for unauthorized warmaking would not. Biden’s no longer in a position to do more than advocate such a move, but it seems to fit with how he described his 2007 impeachment threat: “a prescriptive way to make clear to this man that there will be severe consequences, because [attacking Iran] would be the most dire action we could take at this moment.” Back then, Biden insisted that an unauthorized strike on Iran would be an impeachable offense. Does he still think so today? 

If he got the question, my guess is that Biden would answer, “yes.” Willingness to use the dreaded “I‑word” might help shield the Democratic frontrunner from attacks on his left flank. Of course, given Biden’s service as vice president in an administration that ran roughshod over congressional war powers—that answer might also give rise to some awkward questions. But this is the business he’s chosen.