"Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached." - Manuel II Palelologus
I think it may well be Cantor. All of the other trial balloons that have been floated have been greeted with negative reaction by various factions within the party. The only negative reaction to Cantor has been that he’s relatively unknown. That problem will be solved once he’s nominated.