They didn't reject Him altogether, in spite of the fact that they didn't like Him. They believed Him to be a prophet. They accepted Him as a miracle-worker and healer. The accepted Him as a great teacher. But they did not accept Jesus as Saviour, Lord, and God.
Lordship is where they drew the line.
And their limited acceptance led to total rejection in the end. The people, who were following blindly along, also ended up rejecting Jesus, in spite of the tremendous evidence that He was exactly who He claimed to be. The people were sometimes astonished at the lack of acceptance Jesus found with their leaders, but they continued in the end to follow the leaders they had chosen. Or is it possible to be a Sadducee today, who finds his security in a liberal standard of conduct, who doesn't believe in the resurrection from being spiritually dead and who doesn't accept that God has power for him to overcome sin. Whether you find yourself a Pharisee or Sadducee today, the picture looks pretty black.