“Truly, I say to you, all sins will be forgiven the children of man, and whatever blasphemies they utter, but whoever blasphemes against the Holy Spirit never has forgiveness, but is guilty of an eternal sin”— for they were saying, “He has an unclean spirit.”
Mark 3:28-30 ESV
By saying that Jesus has unclean spirit and that Jesus is driving satan with the power of the demon the Pharisees are in a danger position for they won’t be able to get forgiveness from God. Not trusting Jesus as God’s way of forgiveness puts them in a position where they won’t be forgiven, therefore they are guilty of eternal sin. :(