LIKE Jonathan Bernstein, I think John McCain is wrong when he says that it would set a "catastrophic" precedent for congress to vote down Barack Obama's request for authorisation of the use of military force in Syria. As Mr Bernstein says, "Congress and the president are co-equal. That’s true in general, and it’s true of 'national security matters' in particular." Whether or not to drop bombs on another country with which we're not at war is a pretty darn significant decision, and in a democratic country, it's perfectly normal for the legislature to have an equal say. But then Mr Bernstein goes on to say something that isn't true at all (my emphasis):

A defeat for Obama’s plans will not set any sort of terrible precedent. All it will tell us is some combination of the president having a fairly weak case at this point, or the president having done a bad job of selling his case. To the extent that the former is true, the nation — and in the long run, Obama — are better off if Congress opposes him. To the extent that the latter is true, it will only mean that future presidents have a stronger incentive to sell their policies more broadly, which sure seems like a good consequence to me.

Now hold on a minute. There are many reasons why Congress might vote down Mr Obama's plans that have nothing to do with either the strength of his case, or with his panache in selling it. Mr Obama's case might be airtight, and he might argue it with the eloquence of Daniel Webster and lobby for it with the hard-ball political dexterity of LBJ; and yet a majority in congress could still vote it down because they are delusional, amoral or high on drugs. (We're just speaking hypothetically, here.) To put things less hypothetically, most lawmakers might find that their assessments of the merits of the case, and of the president's convincingness, do not proceed in an airy sunlit realm of pure reason, but are instead influenced by partisan affiliations. Or they might find their judgments affected by political self-interest. In other words, most lawmakers might be human beings like the rest of us.

And indeed they are, as Sarah Binder explains: "Few scholars still believe the adage that 'partisan politics stops at water’s edge.'" She cites William Howell and Jon Pevehouse, who examined the issue in a 2007 book and an article in Foreign Affairs:

The partisan composition of Congress has historically been the decisive factor in determining whether lawmakers will oppose or acquiesce in presidential calls for war. From Harry Truman to Bill Clinton, nearly every U.S. president has learned that members of Congress, and members of the opposition party in particular, are fully capable of interjecting their opinions about proposed and ongoing military ventures. When the opposition party holds a large number of seats or controls one or both chambers of Congress, members routinely challenge the president and step up oversight of foreign conflicts; when the legislative branch is dominated by the president’s party, it generally goes along with the White House.

It's hardly surprising that if you see "not undermining a Republican president" as an important goal, you will be more likely to give his proposal to invade Iraq the benefit of the doubt than if you see "undermining a Republican president" as a neutral or positive outcome.

Now, to say that partisan considerations influence lawmakers' decisions about going to war is not to say that they influence them just as strongly as decisions about, say, universal health care. The aphorism that politics ends at the water's edge isn't really a neutral observation; it's a prescriptive norm. Politicians feel a sense of obligation to discount partisan motives when making decisions about foreign policy, and particularly decisions about using military force. There is a sense that one ought to present a united front. And that instinct is not unfounded. Any group facing negotiations with another group will achieve its aims more effectively if differences are first ironed out in private within the group, rather than blowing up into public arguments during negotiations that can be exploited by the opposing party.* This is true whether the negotiations are between countries, corporations, unions or political parties; for that matter, even individuals will do better in negotiations if they walk in with a clear and settled vision of their demands, rather than allowing themselves to engage in internal equivocation.

And this is where John McCain has a bit of a point. There is a certain ethical sense in American politics that partisanship ought not to affect international security policy. It may not be a rule that's always followed, perhaps not even very often, but there's at least a sense that you ought to be ashamed to admit it if you violate it. In domestic political issues, there's no such norm, and partisanship has at this point almost entirely paralysed American domestic policy. If Congress rejects Mr Obama's case for a limited attack on Syria to punish the government for its use of chemical weapons, that rejection will to some extent reflect partisan considerations, and if we allow the partisan component of such decisions to grow, then we really are weakening America's ability to throw its weight around as a powerful, unified actor in the international security field. I think it's silly for Mr McCain to claim that a "no" vote would weaken America's international security credibility "catastrophically". But it would probably weaken it some, and if you think that's important, it's appropriate to call on members of Congress to be more deferential to the president on this vote than they might be on, say, transportation policy. Though obviously if you think attacking Syria is a disastrous mistake, that's going to be a more important consideration than any need for deference to the president.

* There is a special case in which this is not true: the good cop/bad cop strategy, in which one party can use its own internal divisions between doves and hard-liners as a negotiating tactic to wring cooperation out of the other party. But I don't think America can employ that tactic effectively in the Syrian case.

(Photo credit: AFP)