1) Congressional authorization for this round of air strikes will allow the president to use it as precedent for air strikes on the Assad regime in the future.
2) The country is split on the decision to utilize American air power in Syria. Authorization gives the president and the Democratic party political cover moving into the 2014 & 2016 elections. This also sets a precedent for future U.S. presidents, Democrat or Republican who are dealing with crisis overseas and urged to act swiftly without taking into account whether those actions are a national priority. Those presidents could relieve pressure and safeguard US resources by citing the presidents remarks made today.
By stating air strikes are not time-sensitive, the White House can act based on its own timetable, rather than the rhetoric of Assad, Putin, or pundits across the media.
The president is signaling he will not let the urgent crowd out the important. We have the power to deliberate and execute on behalf of the international community, but also to present our strategic aims thoroughly, not just in the House & Senate but at the G20 to the leaders of other world powers. The U.S. is not ashamed of its position or the action its seeking to undertake, and Assad is powerless to stop it, whether it begins tomorrow or in 10 days.