2) The blank check problem. Lots of lawmakers, Republican and Democrat, believe Obama’s draft resolution gives the president too much power. The draft would grant Obama the authority to use armed force “as he determines to be necessary and appropriate” in connection with weapons of mass destruction in Syria, for the purpose of preventing the future use or spread of those weapons, or, more generally, protecting the U.S. and its allies.

For many lawmakers, that’s too broad a mandate. But a significant number of members might reject even a narrowed version of the resolution on the grounds that, once the use of force is authorized, Congress as a practical matter will have little control over how the president exercises it.

3) The nature of the Syrian opposition. Many Republicans will never be convinced the U.S. can come to the aid of good rebels in Syria without also helping bad rebels in Syria. It’s just too complicated, they believe, and there are simply too many bad guys. Why risk aiding al Qaeda or its affiliates? These Republicans remain unconvinced by arguments from fellow GOP lawmakers like John McCain, who point out that in the Libyan operation the U.S. essentially set up a safe area for good rebels in Benghazi. Given what happened later in that Libyan city, the skeptics will remain unconvinced.