Republican John Boehner and Democrat Nancy Pelosi left the White House today supporting President Obama's plan to punish Syria's use of chemical weapons. But both the parties they lead are sharply divided. So why has the President asked Congress to debate a decision he says he's already made? Without more international backing, does he need time to plead his case to the American people? What if Congress says "no?" What's at stake for American security and international sanctions against weapons of mass destruction?