Ten thoughts on Iran
I strongly agree with Jack Goldsmith that legalistic debates about war are almost entirely besides the point; more than any other issue, decisions about war are almost wholly political. No court is going to stop a war, and I reflexively somewhat discount arguments that label wars "illegal." It might be rhetorically useful, but it's a category error.
In my view, the only hard and fast congressional constraint on war is supply-side; if Congress wants to shut off presidential adventurism, it would need to not annually provide the best military in the history of the world to the executive. That Congress chooses to provide such an army reflects both a sensible reaction to the difference in danger in the world post-WW2 compared to 1789 or 1900, but also guarantees the ability of the president to make limited war absent pre-approval from Congress.
That said, both congressional and public opinion are serious factors in presidential warmaking, affecting all aspects of it: the choice to go to war, the strategies and tactics available, and the will to continue. No presidentially-initiated war can continue if public and/or congressional support is withdrawn, and presidents work extremely hard to maintain the support of both. Bad polls and/or seemingly-symbolic votes in Congress against this current action will narrow the paths available to the administration. It does not take an act of Congress for a war to end against the president's independent judgement.
Given that, it is both surprising and risky that the president and the administration did almost no work to build public opinion or public coalitional support for the war ahead of time. That they have not done much work to define and defend the mission since it began is even more surprising, and more risky. Early signs point to them pehaps paying a public opinion price. It's bad if this is a communication problem; it's much worse if it's a substantive one.
The president's outlook on war feels very Clinton-like to me. He does not seem reluctant at all to engage militarily in wars of choice in general, but seems very hesitant about the introduction of US ground forces. This may very well be a reaction against the lessons of Bush 43 and the Iraq war, much as Clinton's outlook can be read as a reaction against the lessons of Vietnam.
As Nate Silver notes, public opinion about individual military actions has attenuated recently, producing less of a rally-around-the-flag or other positive bump than in the past, but also little discernable drop in support. All that can change if (knock-on-wood) there are significant U.S. casualties or failed objectives, but one ex ante assumption is that, all else equal, any military action will have less medium-term impact on presidential approval than in the past, one way or another, even if the actual military intervention is more popular (or less).
One obvious reason for this is partisan calcification. Another might be fragmented and distributed media. One sensation I had over the weekend was how hard it was to get any news that felt solid, much less objective. Another sensation was how easy it was to shut all war news out. It is clearly not 1990. I would forgive people for not even realizing there was a war on, it is easier than ever to avoid hearing about it.
My baseline assumption is that moral sentiment about war is highly tied up in partisan bias and, within that context, questions about the ability of the administration to properly define achievable objectives and competently execute them. I don't think it's particularly controversial to label the Iranian regime evil or to wish they were gone. I suspect most of the public and elite worry right now is about either the cost of making it happen, or the ability to do so without making things worse. There are short-term answers to these questions we will know within weeks, but also long-term one we won't know for years.
I generally do not believe Wag The Dog style stories about presidents starting military actions to defect public opinion from domestic problems. I did not believe that about Clinton and the so-called Monica Missiles, and I do not believe it about Trump here.
Count me as someone skeptical that the administration has properly thought this through. Conditional on that, I'm probably more optimistic than most that the medium-term result of this will be positive for the US and our allies. Conditional on that, I'm almost certainly more worried about than most about the possibility of this spiraling out of control into a major regional conflict.