Final answer:
The Pharisees claimed that Jesus was casting out demons by the power of Beelzebub, the prince of demons.
Step-by-step explanation:
The Pharisees claimed that Jesus was casting out demons by the power of Beelzebub, the prince of demons.
This can be seen in Matthew 12:22-24: Then a demon-oppressed man who was blind and mute was brought to him, and he healed him, so that the man spoke and saw. And all the people were amazed, and said, “Can this be the Son of David?” But when the Pharisees heard it, they said, “It is only by Beelzebul, the prince of demons, that this man casts out demons.”
So, according to the Pharisees, they believed that Jesus was working with Beelzebub, a powerful demon, to perform the miracles of casting out demons.