Senate Majority Leader Mitch McConnell (R-Ky.) speaks to reporters Tuesday about the vote to advance an amendment that would oppose withdrawal of U.S. troops from Syria and Afghanistan. (J. Scott Applewhite/AP)

On Thursday, the Senate voted 68 to 23 to rebuke President Trump over his decision to pull military forces from Afghanistan and Syria. The vote came after the president’s intelligence chiefs publicly contradicted his assessment of national security threats.

These events reflect both the unusual nature of the Trump administration and longer-term trends in the politics of national security.

Here are three takeaways.

1. The national security oversight process is broken — but that started long before Trump.

These were two very public — and unusual — rebukes of the president, which don’t usually come from inside his administration or from the Senate. But they do little to alter the trend of declining constraints on U.S. presidents’ power to set foreign policy.

As political scientist Linda Fowler’s research has shown, congressional oversight of foreign policy has declined dramatically since the end of the Cold War. The Senate Foreign Relations and Armed Services committees have held markedly fewer hearings over time. Think about how this week’s rebuke of the president came about. Instead of building to this point through hearings that bring administration officials to Capitol Hill to explain U.S. goals in Afghanistan and Syria, Senate Majority Leader Mitch McConnell (R-Ky.) entered the debate publicly only after the president had announced and implemented his decision.

That makes the vote on McConnell’s amendment the exception that proves the rule, not a firm reassertion of congressional authority on foreign policy.

2. Trump might have avoided this.

Still, it is significant that Trump’s intelligence chiefs offered public testimony that contradicted many of the president’s views. What’s more, McConnell was the one who sponsored the amendment challenging the president’s policies on Syria and Afghanistan. More often, the majority leader carries water for the president when his party holds the White House. In fact, McConnell has generally been reluctant to confront Trump, much less hold votes that put Senate Republicans at odds with the president.

While Congress’s visible oversight has diminished over time, in the Trump era, normally invisible constraints on the president have also broken down. Typically, the head of the CIA and the director of national intelligence would be more confident that the president would pay attention to their views in private. But Trump has shown little interest in what other people tell him. And unlike Trump, most presidents two years into their terms have normally developed relationships with lawmakers that would help them read the congressional mood more effectively.

This week was only the latest episode that demonstrated that Trump has not effectively used the tools he has to manage his administration’s relationship with Congress on national security policy. As one of us, Elizabeth Saunders, noted in December here at TMC, the way Trump responded to the killing of Jamal Khashoggi in the Saudi Consulate in Turkey increased his political costs for pursuing his preferred foreign policy. Trump sent then-Defense Secretary Jim Mattis and Secretary of State Mike Pompeo to testify about possible Saudi involvement, but the Senate didn’t buy their defense of Saudi Crown Prince Mohammed bin Salman and demanded to hear from CIA Director Gina Haspel.

When Haspel finally testified, GOP senators such as Lindsey O. Graham (S.C.) and Bob Corker (Tenn.) made clear they held the crown prince responsible for Khashoggi’s killing, in direct and public contradiction of Trump’s view. Not only that, but Corker led the Senate to vote to hold Mohammed personally responsible for the killing. As one of us, Sarah Binder, noted here at TMC, that and another measure didn’t go anywhere, but the rebuke was still startling.

Such events are rare because presidents typically work hard to avoid them. Instead, Trump is failing to build support for his policies, within his own team and with Congress. One could imagine that if the Trump administration wanted to pull out of Syria and Afghanistan, it could lay the groundwork with back-channel reassurances to Congress about how the plans would address U.S. commitments to allies in the region or remaining counterterrorism concerns.

Instead, Trump has faced a series of public rebukes. First, Mattis resigned in a public break with Trump, partly driven by these policies — raising concerns in the national security establishment and abroad because many viewed him as the last remaining “adult in the room.”

Second, the intelligence chiefs’ testimony noted that the Islamic State was still a threat. And third, McConnell brought his amendment to the floor. Republicans like McConnell might be more hawkish on national security than Trump, but they have acquiesced to the president on other policies. Allaying at least some of these concerns might have gotten Trump much of what he wanted while preventing a vote — something senators typically like to avoid on national security issues, after all.

3. Shocked, shocked to find politics going on here!

Notably, the vote generated interesting party alignments. Republicans lined up nearly lock-step behind McConnell, while the vote cleaved Democrats down the middle. Whether or not Republicans anticipated the Democratic split, a vote that unifies the majority party while airing minority-party divisions is a win-win for the majority.

GOP unity this time, however, is less remarkable than it might seem. This was a procedural vote on a provision that will have no direct policy consequence for the administration. Still, it might be politically valuable to Republicans: It allows GOP senators to go on record — at little real cost — endorsing a core Republican position in favor of a robust U.S. military posture abroad.

Democrats meanwhile split 25-20 in favor of criticizing Trump’s policy, probably reflecting ideological and partisan commitments. More moderate senators tended to side with Republicans challenging Trump, even after adjusting for Trump’s 2016 performance in their states. Opponents — including four progressive Democrats who have launched presidential bids for 2020 — staked out the antiwar position popular across the Democratic base, even at the cost of appearing to side with the president.

These alignments reversed what we saw twice last month. First, in December, Democrats voted to order the president to end U.S. military operations in the Saudi-led war in Yemen, while just seven GOP senators joined them. Second, last month, 22 Republicans cast the only “no” votes in a recent House effort to keep Trump from withdrawing the United States from NATO.

We are seeing yet again that Trump’s national security decisions are upsetting allies abroad and partisans at home — and the president is doing little to prevent it.

James Goldgeier is a professor of International Relations at American University, visiting senior fellow at the Council on Foreign Relations, and the 2018-19 Library of Congress chair in U.S.-Russia relations.