President Trump’s decision to order the assassination of Iranian Quds Force commander Qasem Soleimani, a major escalation that could unleash all sorts of bloody and terrifying consequences, should prompt Democrats to do two things without delay.

First, all the 2020 presidential candidates should reaffirm their commitment to reining in the war powers of the president, which presidents in both parties have abused for decades.

Second, congressional Democrats should revisit the failure of the Senate last spring to pass a measure that would have required Trump to seek congressional authorization for military action against Iran.

More broadly, they should reinvigorate the debate over the need to restore the warmaking power to Congress. Trump’s strike, which killed Soleimani near Baghdad International Airport, raises the prospect of a major escalation, and Congress must assert that authority lest Trump seek to escalate without their approval.

The failure of that vote last spring is looking particularly fateful right now. The measure, which was introduced by Sen. Tom Udall (D-N.M.) failed largely along party lines, with all but one (absent) Democrat voting for it and all but four Republicans voting against it.

Let’s also revisit the fact that as this measure was voted down, Senate Majority Leader Mitch McConnell (R-Ky.) assured us it wasn’t necessary.

“The president made it absolutely clear that he is not interested in starting a war with Iran,” McConnell told reporters in June. “Everybody ought to take a deep breath.”

Maybe the Senate shouldn’t have taken a deep breath.

An assassination without congressional approval

In saying that, McConnell was helping do the bidding of Trump, who claimed at the time that he didn’t need congressional approval to strike Iran. The debate over that measure came when Trump ordered an Iran strike after the downing of a U.S. surveillance drone but reversed it.

This time, however, Trump has ordered the assassination of a top Iranian military commander without congressional authorization.

Sen. Chris Murphy (D-Conn.) told me that Trump probably would have gone forward with this strike without authorization even if a measure like the Udall one was in place by claiming it’s not an initiation of hostilities but rather a preemptive defense of U.S. troops. The administration is claiming the strike was a “defensive action.”

But as The Post notes, the basis for that assertion is “unclear.” And having a measure like this in place might have compelled the administration to better justify its claim along those lines.

Murphy noted that the killing of Soleimani blurred the distinction between a warlike and a defensive action.

“It’s not clear whether it was defensive in nature or a declaration of war,” Murphy told me. “If a foreign country assassinated our secretary of defense, we would unquestionably consider that an act of war that demanded a disproportionate response.”

Murphy added that the defensive authority Trump is apparently relying on is “nebulous” and that this requires Congress to make it absolutely clear that no further escalation can go forward without its approval.

“We now have to have a debate in Congress about whether or not we’re prepared to give the president military authority against Iran,” Murphy told me.

Murphy said that Democrats can pursue this in two ways. First, they can try to push for another vote on a measure like the Udall amendment. And second, they can prod Congress to reassert its authority under an already existing statute, the War Powers Act of 1973, which has been triggered by Trump’s action and requires him to seek congressional authorization for future action.

“The president has legal obligations to come to Congress for authorization to take any future military activity against Iran,” Murphy told me. “Congress has the ability to go to court to enforce those provisions if he doesn’t comply.”

It’s particularly urgent that Congress assert its authority, because the killing of Soleimani, an enormously influential figure in the region, could result in a continued escalation of hostilities, experts are warning. As Andrew Exum, a former deputy assistant secretary of defense for Mideast policy, puts it:

The United States is now in a hot war with Iran after having waged war via proxies for the past several decades. This doesn’t mean war, it will not lead to war, and it doesn’t risk war. None of that. It is war.

What’s more, as Dan Drezner points out, we still don’t know how this decision was made, and given what we know about Trump, it might have been an impulsive one, without any serious planning for the aftermath or for a big escalation.

All of these reasons, among others, are exactly why Congress needs to assert its control over Trump’s warmaking authority.

Republicans, of course, are largely content to grant Trump this authority and are supporting Trump’s strike. By contrast, many Democrats are demanding to know whether Trump has planned for the consequences and are calling on him to fully brief Congress.

The 2020 Democrats should step up

Administration officials have asserted that Trump might have the power to go to war with Iran under the 2001 Authorization for Use of Military Force, in which Congress empowered the president to go after those involved in 9/11. That’s an absurdly strained reading of the AUMF.

But President Barack Obama also repeatedly abused the war power, for instance by citing the same absurd justification for war against the Islamic State.

That legacy is one reason why all the 2020 candidates should reaffirm support for the idea that the warmaking power rests with Congress. Numerous candidates have done this — Sen. Bernie Sanders (I-Vt.) more forcefully and Joe Biden less so — but now is the time for them to reiterate their pledges not to abuse this power.

“It would be wise for all the Democrats running for president today to reaffirm their support for the War Powers Act and their intention to comply with it,” Murphy told me. “That would put additional pressure on the president to comply."

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