The Catholic Church and other religious groups are mobilizing against the right-to-die legislation ahead of a hearing Tuesday in the Assembly Health Committee.
The bill's authors already postponed the vote because they didn't have enough support for it from fellow Democrats.
The holdouts include lawmakers from heavily Catholic districts in the Los Angeles area, where the archdiocese opposes the bill.
Right-to-die advocates hoped their efforts would be helped by the publicity surrounding Brittany Maynard, who moved from California to Oregon to end her life in November. Despite bills in several states, none has passed right-to-die legislation this year.