My understanding is that it takes a 2/3 majority vote of who is in attendance for the vote. So if O wants to push it through he can covertly schedule the vote....
I wouldn’t put it past him...
So, the vote is scheduled for some well-chosen moment, it gets "legally" passed and then the Repubs can safely say "Oh well, it was all done according to the constitution. We don't like it one little bit but we'll just have to live with it now."