The first, which many have remarked on, is buy-in: If Congress votes for a policy, it may make it more difficult for members of Congress to be critical if things go wrong. There may be something to it, but I’m somewhat skeptical of it. From this point of view, there’s also a risk that Congress — or a significant portion of it — will vote against the policy; not only could that make them even more likely to speak out against it down the road, but also it could lead to Congress blocking the policy altogether. Moreover: Does anyone really think that today’s Republican Party will hesitate to turn against a messy intervention even if they previously supported it? After all, Democrats did so when George W. Bush was president. So if that’s the reason, then I think presidents should resist consulting with Congress.
However, there’s also a very good reason: Going to Congress is an excellent way of generating information, and presidents should always, always, always be seeking out information.
Presidents risk being prisoners to their administrations. It’s really hard to break out of that, especially on foreign policy and national security questions, where administration experts are going to insist on, well, their expertise. Going to Congress, however, breaks out of it. The way that members react will furnish highly useful clues to the president about sentiment in the nation and among various organized groups. Even more helpful, congressional opponents and skeptics have an interest in finding the sharpest arguments to make against an intervention — arguments which, then, the administration must answer. Which, in turn, unearths additional information that the president might not have learned, otherwise.
Of course, the risk in all of this is that the president may learn that the proposed military action isn’t as good an idea as it seemed. A smart president, at that point, will modify the plans! The other option — the one that Bush followed in 2002 — is to lie and bully through Congress. And we saw how that turned out.
In other words: Congressional hearings before the Iraq War revealed that the administration was seriously low-balling it’s estimates of the difficulties of a postwar occupation. Because Bush and his White House treated that as a problem of inconvenient spin, it didn’t do them any good. But a better president would have realized that the problem was substance, not spin, and that it couldn’t be wished away.
Now, none of this means that President Obama should necessarily seek Congressional votes for a small-scale military intervention; there are counter-pressures involving, for example, a possible preference for moving quickly. And then there’s the problem with Congress’s dysfunction.
But in general, presidents should value the information that can be learned by going through a (mostly) public defense of military action before it begins.