Congress should reject anything short of regime change. Sharing blame for a symbolic action made necessary by the President's imprudent red line will not help Congress.
A humanitarian and strategic case can be made for crippling strike combined with aid for the non-ideological rebels. Obama could make that case to Congress, the US citizenry, and the world but his heart is not in that option. He hasn't even delivered the small arms that were promised months ago.
Politically, appealing to Congress has its advantages. The hawks will not vote for a symbolic strike and the doves will not vote for any action. There will be less fall-out if the measure fails in Congress than if Obama launches it and Syria continues to use poison gas.
It is also possible that the President knows that the actions he has planned will be symbolic and will not change the balance of power in the area.
The President knows that any action he takes in Syria will be unpopular, especially with the anti-war base that the Democrats milked for support during the Bush years. In a bit of irony, there were anti-war protests outside of Secretary of State Kerry's house over the weekend. This is the same Kerry who first made his name as a Viet Nam protestor.
Last week it was assumed that he would order a strike with cruise missiles and that this would be limited. At the last minute he decided to wait and ask Congress for permission. While this move was applauded by many, this move was more likely motivated by a desire to share the blame than by a desire to observe Constitutional requirements. This is the same president who ignored Congress and the War Powers act in Libya.
Now Syria has crossed the red line (by some reports they have been crossing it on ever-expanding scale for months). The President feels that he has to act but has not good options. There is no support for a boots-on-the-ground approach. Even an air attack has limited support.
When he drew his red line, the President does not appear to have consulted with any allies or members of Congress. There are rumors that he did not even consult with the State Department. He warned of serious consequences but did not give any specifics and possibly did not have any in mind.
President Obama has painted himself into a corner on Syria. Elected on an anti-war platform, he is reluctant to get involved in new wars. He reluctantly got involved in Libya only after being shamed into it by the European countries. With the exception of France, they are sitting out this conflict so there is no "leading from behind".For more than two years Obama insulated himself from the war with his "red line" which implied that Syria could slaughter as many of its people as it wanted as long as it was done with conventional weapons. He obviously expected that a warning about chemical weapons would be enough.
The President made it clear that he believes that he has the authority to order the strike regardless of Congress. If so then he should either act on that or back down instead of trying to share the blame.