Matthew 9:34 But the Pharisees said, “By the prince of the demons, he casts out demons.”

Matthew 10:25  . . . If they have called the master of the house Beelzebul . . .

Matthew 12:24 But when the Pharisees heard it, they said, “This man does not cast out demons, except by Beelzebul, the prince of the demons.”

Mark 3:21 When his friends heard it, they went out to seize him: for they said, “He is insane.”

Mark 3:22 The scribes who came down from Jerusalem said, “He has Beelzebul,” and, “By the prince of the demons he casts out the demons.”

Mark 3:30 because they said, “He has an unclean spirit.”

Luke 11:15 But some of them said, “He casts out demons by Beelzebul, the prince of the demons.” . . .

John 7:20 The multitude answered, “You have a demon! Who seeks to kill you?”

John 8:48 Then the Jews answered him, “Don’t we say well that you are a Samaritan, and have a demon?”

John 8:52 Then the Jews said to him, “Now we know that you have a demon. Abraham died, and the prophets; and you say, ‘If a man keeps my word, he will never taste of death.’”

John 10:20-21 Many of them said, “He has a demon, and is insane! Why do you listen to him?” Others said, “These are not the sayings of one possessed by a demon. It isn’t possible for a demon to open the eyes of the blind, is it?”

Note how the second half of the last quote seems to indicate that some genuinely believed Jesus was “demon-possessed and is insane”.