Credit: George Danby

During the Democratic presidential debate on Thursday night, only the scantest attention was devoted to an enormously important question: whether the next Democratic president will return the authority to declare war to Congress, where it belongs. Joe Biden and Sen. Bernie Sanders, I-Vermont, both alluded obliquely to the need for presidents not to abuse that power, but little more was said on the matter.

As it happens, the Senate just concluded voting on the question of whether President Donald Trump should go to war with Iran without congressional approval. The measure failed to get the 60 votes it needed for passage.

But it did get 50 votes — which is to say that half the Senate is on record against this. That’s not insignificant as a statement, even if it won’t necessarily stop Trump from taking the plunge.

The measure in question is an amendment to a defense bill offered by Sen. Tom Udall, D-New Mexico. Here are the guts of it:

“No funds may be used to conduct hostilities against the Government of Iran, against the Armed Forces of Iran, or in the territory of Iran, except pursuant to an Act or a joint resolution of Congress specifically authorizing such hostilities that is enacted after the date of the enactment of this Act.”

Four GOP senators supported the amendment, along with 46 of the 47 Democratic senators (one was a no-show).

Trump recently declared that he has the power to strike Iran without congressional authority. Lawmakers have struggled to get administration officials to clarify the basis for this authority, with one claiming that “we will comply with the law,” but without further clarification.

It appears the administration is likely to claim authority from the 2001 Authorization for the Use of Military Force, in which Congress empowered the president to use force against those he “determines planned, authorized, committed, or aided” the 9/11 attacks.

The idea that this might authorize war with Iran is based on an absurdly strained reading of the Authorization for the Use of Military Force, just as it was absurd when former President Barack Obama cited it to justify war against the Islamic State group. Thus the push for a vote in the Senate to try to block Trump from claiming this authority.

It’s worth noting, as a Democratic aide points out, that multiple Republicans resisted even having a vote on this at all. But Senate Democrats, rallied by Minority Leader Chuck Schumer, New York, threatened to hold up the defense bill and managed to get Senate Majority Leader Mitch McConnell to agree to one.

This is the first time that the Senate has weighed in on this question, and now half the upper chamber has declared that Trump should not go to war with Iran without congressional authorization. It would have been 51 with the no-show Democrat, who put out a statement in opposition as well, prompting Schumer to remark: “A bipartisan majority of the Senate today sent an important message to President Trump: you do not have a blank check to pursue another endless war in the Middle East.”

A vote in the House should follow in the coming days.

Trump, as you may know, already vetoed a separate resolution that would have ended U.S. support for the Saudi-led war in Yemen, which has produced a rolling humanitarian disaster. Trump’s implementation of this war without congressional authorization is also absurd, just as it was a mistake when Obama first initiated a more limited version of this operation without such authorization. Indeed, one top Obama adviser recently conceded to the Nation’s David Klion that this was ill conceived.

The resolution that Trump vetoed also stated that “Congress has the sole power to declare war,” and it had passed both chambers, even picking up seven Republicans in the Senate.

So the Senate has now twice rebuked Trump’s abuse (or, in the case of Iran, threatened abuse) of the warmaking authority. That’s something, though it isn’t enough to stop it.

This is why I keep arguing that the Democratic candidates should be talking more about this — they should be uniformly pledging that as president, they would return the warmaking authority to Congress. This would ideally entail a frank discussion of how both parties have been complicit in the erosion of that authority.

Meanwhile, the abuses continue.

Greg Sargent writes The Plum Line blog. He joined The Post in 2010, after stints at Talking Points Memo, New York Magazine and the New York Observer.