It requires a lot of political courage to risk a public rejection, especially when the decision is believed to be right but known to be unpopular with the public, many allies and top military leaders. There is a special problem when the Security Council is divided on an issue the United States considers crucial and when our NATO allies refuse to take a stand. It is well known that some of the president’s political adversaries will not support any conceivable proposal he might make, that dovish members of Congress are likely to oppose military action and that some congressional hawks want strong and sustained action to change the course of the Syrian civil war. Going ahead with limited military action after a rejection by Congress would amplify many of these critical voices.

The president has wisely refused to answer media questions about how he would proceed if his efforts failed in Congress. If and when a vote takes place, there will be many factors involved, but the assumption of compliance is best because supportive votes would be lost by the president saying he would ignore a negative vote. Many legislators will be looking, at least in part, for popularity with constituents who strongly oppose using force. For those who are eager to see a strike against Syria, a presidential pledge to attack without approval would make it possible to achieve their objective without alienating voters back home. And for those who oppose military action but are willing to alienate constituents because of loyalty to the president, his pledge to ignore a congressional decision might lessen their commitment to him.