After pledging so strongly to take action and then failing to receive British support, I think this is the President's way of backing off without looking like it. If the "strongest ally" is polling at 64% against, your prospects don't exactly look good... The other thing to consider is the precedent he's setting. Trying to move away from the Bush-era unauthorized military strikes his previous policy of using unauthorized force, such as the use of drone strikes abroad and military intervention in Libya is certainly commendable, but it's also a CYA. If Congress gives him the green light and five years down the road we're still involved, he and the Dems might be able to get away with "But Congress said it was okay!" For the wallet's sake, hopefully that's not the case, but you can never be too sure. Anyway, it's certainly adhering more to the spirit of the Constitutional powers, i.e. no war without Congressional approval, but whether or not that was his true and sole intent is in doubt.