I don't think the Constitutional option will be needed. I think the Democrat members of the gang of 14 will have to step to the plate and vote yes on cloture. If they stay committed to their original vow, no problem.
DiFi is one of the Gang of 14 and we already know Cindy Sheehan forced her to roll over and Kenndy is a Gang of 14 and rolled over and I don't trust McCain (who is/was in Davos) any farther than I could throw him.