31 In the same way the chief priests, along with the scribes, were also mocking him among themselves and saying, “He saved others; he cannot save himself. 32 Let the Messiah, the King of Israel, come down from the cross now, so that we may see and believe.” Those who were crucified with him also taunted him.
It can seem that the pharisees agree that Jesus ''saved others'' (and to that extent he would be already the Messiah and the king of Israel, according to pharisees). Only, they disagree about his ability to save himself. If Jesus comes down from the cross, then he would prove that he is able to save himself, and not only ''others''.
This may explain why the motivation behind the pharisees, according to Pilate (and ''Mark'' himself!) is ''jealousy'':
10 For he realized that it was out of jealousy that the chief priests had handed him over.
In short, the pharisees see (and agree) that Jesus seems really the Messiah, but they are jealous of him because they don't want a Messiah who cannot save himself: the weakness of Jesus as Messiah is the weakness of them, as believers in Jesus the Christ.