Based on what he has said I think he has to do something, even if he only gets the Senate to approve.

King is at least partly fos as are most congressmen. The idea that he is undermining future exec authority is ridiculous. Over the centuries, there has been too many exceptions for any potus in this era to set precedents. Potus tend to do what they want to do within reason, determined by their popularity, and political considerations.

I do think he takes a huge hit if he is stymied by Congress, and worse if Assad kills another thousand while Obama pats his foot. I actually think Assad will be afraid to use chems again. This "crisis" may be sufficient to make him hesitate for the short term. Long term is a different matter that depends on how the rebels fare.

Bottom line imo, none of it is about saving lives or doing then right thing. It is all political maneuvers