I agree with much of Matt Purple's analysis of American options in Syria, but let me offer a couple of modest points of disagreement.
First, I don't think even the "idealist" aka McCain-Graham solution involves boots on the ground.
Second, I don't hate choice #2 as much as Matt does. The idea of Hezbollah and al Qaeda members killing each other does my heart good, though I understand it's not really a long-term strategy. Steve Hayes mentioned on Fox News this evening that supporting #2 might actually lead to at least one of our enemies ending the civil war stronger than they otherwise might.
The reason that #5, i.e. do nothing, probably won't happen and, unfortunately, probably shouldn't happen is because our naive, incompetent president at least twice talked about a red line which Assad has not thoroughly crossed more than once. If we have any influence left in the Middle East, which is perhaps doubtful, it will entirely be gone, at least while Obama is president, if we do nothing.
So, while I agree that #4 is probably most likely, I would offer an alternative, in the spirit of Ronald Reagan in 1986: Send a couple of missiles into Assad's home. Kill a couple of his kids, just as he's done to hundreds of his own citizens' children. And then let him know that the next time, we won't play so nice. Qadaffi sure responded to that sort of approach...