USA Today has polled all members of congress as to their current position on an AUMF for Syria. Overwhelmingly the response is undecided. Here is a nicely laid out graphic of where things in the Senate and House stand by party.
There is a bloc of Republican house members that are firm no. What seems to be significant is that Democrats are not falling into line behind the president. They are getting an ear full from their constituents and their political instincts for self preservation are twitching.
The administration has been pouring on the hard sell for over a week and this is as far as they have gotten. They clearly have not sold the American public on their plan. Unless there is some dramatic change in events in the next few days, the changes for success look decidedly slim. It is to be hoped that they have concocted a plan B, because it looks like they are going to need it.