I have a bad feeling this is all just for show.
Nope, this is all about CYA.
1. Congress says yes. The attack results in something positive.
Obama: "Look what I did. Just like when I killed Osama!"
2. Congress says yes. The attack is a clusterfrick.
Obama: "I knew this was a bad idea, but Congress insisted on it when they voted."
3. Congress says no. Obama will not attack.
Obama: "I really wanted to kick their ass. But Congress said no. So, if further gassing happens, it's on Congress not me."