Obama draws a red line in the sand regarding chemical weapons use. Bashir Assad crosses that line. Twice. Then, Obama tries to hem and haw his way out of committing to what he had threatened. Now, Obama has punted the whole thing to congress. Why? The answer is obvious. Obama doesn't want to actually do anything about Syria, but his inaction is making him look bad domestically. Even Democrats are starting to get fed up. So, what's a dilettante with no interest in foreign policy and no understanding of how to make things work in the real world to do? You set yourself up for failure. You punt the whole thing to congress, and then go golfing. If congress votes to use force, it's not Obama's war, it's, well, congress' war, and you know who has the majority in the house. And if they don't, well, sorry all of you Syrian chemical weapon victims, but we tried. It was those nasty Republicans who wouldn't let America do the right thing. But, no matter which way it goes, he's off the hook. This is how a president votes "present."
BTW, I'm not arguing for or against bombing Syria. At this point, anything that we do is going to fail, because the leadership isn't there. A pinprick bombing won't hurt Assad (and actually helps him by letting him claim that he's defied the might of the US), a sustained campaign requires leadership that Obama cannot and will not exercise, and taking no action makes us look feckless and weak.
No matter what action the US takes, we cannot win. That's what comes of voting "present" instead of leading.