President Trump last week ordered a drone strike that killed Iranian Quds Force commander Qasem Soleimani, escalating tensions between the U.S. and Iran. Trump acted without informing members of Congress or seeking their approval.

Although the administration has given Congress its justification for the strike, as required by law, that document is classified — and so we still don’t know the precise legal justification. The president’s lawyers probably point to the 2001 or 2002 Authorizations to Use Military Force (AUMFs) that presidents of both parties have used to wage war for almost two decades. Both AUMFs are broad and somewhat ambiguous, and many critics suggest that using them to justify the Soleimani killing would be legally shaky.

So what comes next in D.C.? Congress could repeal the AUMFs or replace them with a more circumscribed authorization for future military engagements in the Middle East. In fact, last summer, a bipartisan coalition in both the House and Senate, worried that Trump might rush to war against Iran without seeking congressional approval, tried to limit his authority to unilaterally order military strikes against Iran. Among the Republicans who supported the measure was one of the president’s current cheerleaders-in-chief against impeachment, Florida Rep. Matt Gaetz. The amendments passed the House and received 50 votes in the Senate, but failed to secure the 60 votes needed to overcome a filibuster.

Congress probably won’t limit presidential wartime authority — even though opinion polls, including in many swing states, suggest that most Americans want Congress to rein in the president’s war powers.

Here’s why.

Why presidents want AUMFs

The Constitution’s declare-war clause would seem to put Congress in charge on questions of war and peace. But since the Korean War, presidents have routinely asserted independent constitutional authority to order U.S. troops into combat without asking for congressional approval.

Indeed, even when asking Congress to authorize the use of force in specific cases, presidents routinely argue that while they would appreciate it, they do not need congressional approval.

Why, then, do presidents value congressional authorizations? They give presidents valuable political cover. If Congress authorized military action, members have a harder time criticizing presidential policies later, if the effort costs more or lasts longer than promised. President Barack Obama pointed to this dynamic when he delayed responding to Syrian President Bashar al-Assad’s use of chemical weapons. He wanted Congress publicly on record backing the mission and not “sniping” on the sidelines.

When does Congress support the president’s military actions?

Do authorizations really encourage members to rally around the president or at least mute their criticism? To find out, I undertook statistical analyses of how lawmakers responded to a range of military engagements from Lebanon in the 1980s to Iraq in the 2000s. I found that lawmakers who voted to authorize the use of force were less likely to publicly criticize it or vote to curtail it as time passed, even after controlling for their party affiliation, how many of their constituents died in the conflict and several other factors.

To be sure, some who voted to authorize force eventually disavowed their earlier position and criticized military action. But that public reversal can undermine their credibility.

For instance, during the 2004 presidential campaign, John F. Kerry was regularly criticized for “flip-flopping” and inconsistency on the second Bush administration’s war in Iraq, having voted to authorize it in 2002 before striking a more critical tone when seeking the presidency in 2004. In 2008, Obama pummeled his main rivals, Hillary Clinton and John Edwards, for their 2002 votes to authorize the Iraq War, using those votes to question their antiwar credentials.

Even today, after the Soleimani strike, former vice president Joe Biden’s rivals routinely point to his vote to authorize the Iraq War — cast nearly 20 years ago, now — to argue that while he may have national security experience, his instincts are wrong for our era.

Trump’s GOP partisans will rally to his side

Congressional Republicans will probably want to give Trump that valuable political cover, since Democrats have already made clear that they will not. Since control of the House and Senate is divided between the two parties, don’t expect action on updating the AUMFs — whether that’s to authorize or deauthorize military action against Iran.

That’s not surprising, since partisanship today drives most congressional behavior, even in foreign policy. But even during the Cold War, when the two parties allegedly joined to constrain the Soviet Union and its allies, partisan politics rarely “stopped at the water’s edge,” as the truism had it. Since the end of World War II, the size and strength of the president’s party in Congress has been among the most important predictors of how the president will use military force.

When the opposition party’s ranks are strong, it will use various tools — from floor debates to investigative oversight — to constrain presidential military policies. These efforts to raise the political costs of military action often succeed in reducing the scope, scale or duration of American military actions.

By contrast, when the president’s party controls Congress, that party’s leaders repeatedly block efforts to claw back or constrain the executive’s use of war powers.

Lawmakers would rather let presidents shoulder any blame

Even if Congress managed to repeal the AUMFs still on the books, what would it replace them with? Repealing can be easy; replacing, not so much.

Members of Congress like to say they want to be involved in any decision to use force. But lawmakers do not necessarily want to define how their branch should be involved. As events unfold, most members find it is easier to let the president take responsibility for any decisions — while they react.

If the president takes the lead and a military venture goes well, members from both parties can publicly rally behind it. If a mission fails to meet expectations, members of the president’s party can remain silent or even try to distance themselves from the administration’s policies. Meanwhile, members of the opposition party can attack the president — weakening public support for the president’s war and ratcheting up the political costs on the White House for staying the course. Either way, Congress remains potentially influential, without having to suffer the consequences of going on record for or against any particular action.

That’s not what the Constitution’s Framers had in mind. However, so long as lawmakers see the political benefits of a stalemate, Congress is unlikely to revamp the AUMFs.

Douglas L. Kriner is the Clinton Rossiter Professor of American Institutions at Cornell University.

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