President Obama has rarely had problems making unilateral decisions. In fact, he has been more than willing to implement policies even after they were overturned by another branch of government. Furthermore, he has also allowed agencies to do things in disregard of Congressional oversight. We have even seen this in his military decisions as well, with the indiscriminate use of drones and other actions, without the approval and with little consultation from Congress.
The "drum beat" for military action has been loud since it became clear that Syria used chemical weapons on its own people, including hundreds of babies and children. David Cameron, the UK Prime Minister and the United States' strongest ally, called for a special session of Parliament and the members voted against military action. This was shocking and a blow to Cameron's leadership. Meanwhile, France has said it is going to support military action against Syria. President Obama has said that it is "imperative" for the U.S. to attack or we can expect more heinous actions on the part of the Syrian regime. Now, in what could be seen as a "reversal" for a man who has rarely been interested in the legislative branch and its opinions, Obama is not only consulting Congress on the issue of Syria, but asking for them to vote on it.
Political observers are going to be asking questions. Is the president looking for an excuse not to act? Will a negative vote from Congress become grounds for inaction? This is unlikely, because he indicated that there would be action regardless of the vote, but it could significantly affect what that action looks like. Remember, George Bush asked Congress to vote on the automobile industry bailout, they did with a resounding "no" and Bush authorized it anyway with TARP dollars. Actions such as these are often more show than substance. Will a vote in favor of military action lead to more drastic actions by the United States? We will have to wait and see.
If Congress authorizes action, the American people will certainly be more supportive and the president will also be seen as having had "matured" in his decision making. But if the president goes to Congress and they vote "no" and he proceeds with action (as it appears likely), I expect a fairly loud outcry and even more cynicism towards our government and its leaders. A vote supporting the president is anything but guaranteed. The American people have grown tired of war, this includes individuals that have often been sympathetic of the U.S. as the "world's police force." Furthermore, there is something disconcerting about action in Syria to virtually everyone of every political stripe. The regime is terrible in that country, as was often the case in other nations that were overthrown during the "Arab Spring." Sadly, those regimes were often replaced with governments that were more horrific and totalitarian.
Neoconservatives, who have the strongest tendency to vote "yes" to a military action such as that being proposed by Obama, are possibly the least likely to do so when it comes to a state like Syria. This isn't because of any love for the Assad regime, but because the Coptic Christians have come out supporting Assad, since at least he oppresses people equally. Coptic Christians have many sympathizers among conservatives of all types in Congress and they saw that, in Egypt, that the Arab Spring led to the systematic persecution of Christians, particularly among their own numbers. Furthermore, neoconservatives are strongly interested in the safety of Israel, and there are few that believe that country is better off since the Arab Spring. The departure of Assad will likely lead to the rise of the Muslim Brotherhood. Meanwhile, most Democrats are naturally doves and those on the far left are consistently opposed to military action regardless of the circumstances. The growing "libertarian wing" of the GOP are naturally demanding inaction by the U.S. while many in the Tea Party branch cannot seem to understand why this administration is concerned about Syria with a $17 trillion debt. There are few Congressional factions left in either House to validate the President's request.
Still, inaction does not appear to be an option if Obama is going to maintain any international credibility. You cannot, as president of the most powerful country on the face of the earth, draw "red lines" in the sand and ignore them when they are blatantly violated. Yet, he must balance that with an understanding of the temperament of a battle weary nation, if President Obama is going to maintain any credibility at home.