“I put it before Congress because I could not honestly claim that the threat posed by Assad’s use of chemical weapons on innocent civilians and women and children posed an imminent, direct threat to the United States.”
By making that admission, the president highlighted the political problem he faces winning support for his mission. According to polls, the biggest fear people have about a U.S. strike on Syria is that it will lead to retaliation and wider war.
There is no way to help people put away that fear.
Repeating the words “limited,” “targeted,” and "no boots on the ground" is not working. For good reason.
Since the president can't use the most powerful argument, he and his advisers are offering an amalgamated case—one part national security threat, one part emotional outrage at the indiscriminate gassing of children, a dash of fear over lost U.S. credibility, and a smidgen of patriotism.
Democrats who are cajoled "vote for the mission or it will ruin the Obama presidency" might feel political sympathy but it's not an argument lawmakers can replay to their constituents.
http://www.slate.com/articles/news_and_politics/politics/2013/09/barack_obama_s_case_for_striking_syria_the_president_s_arguments_for_military.html