...Ehrman theorizes that what Judas betrayed to the authorities was that Jesus was calling himself king of the Jews, God's anointed, the Messiah or Christ. Ehrman says that Jesus didn't state this publicly, so it was a secret among the Twelve that Judas betrayed to the authorities.
... In Mark, the earliest of the gospels, we have this exchange between Jesus and the high priest (Mk. 14:61b, 62):
Again the high priest asked him, "Are you the Christ, the Son of the Blessed? And Jesus said, "I am; and you will see the Son of man sitting at the right hand of Power, and coming with the clouds of heaven."
Here, it would seem that the "Son of the Blessed," i.e. the "Son of God," is equated with being the Christ. Thus, it seems to me that Ehrman is splitting hairs to make calling himself the Christ / Messiah / King of the Jews as being a different claim from that of being the Son of God. After all, the Messiah (Gr. Christos) was supposed to be God's anointed, which means a king. So, claiming to be the Son of God was the same as claiming to be the Christ, which is the same as being the king of the Jews.
Of course, if one takes the gospel accounts to any degree seriously, Jesus has indeed made a very public claim to being king on Palm Sunday, when he enters Jerusalem in a way that fulfills a messianic prophecy in Zechariah and is hailed by multitudes crying "Hosannah!" This means "Save us," and, by extension, "Free us." Of course, this episode is most likely fiction. However, if we take this as fiction, how can we then turn around and say that the gospels are authoritative if they say that Jesus never openly claimed to be the king of the Jews?
Ehrman also says that Jesus, once arrested couldn't deny the charge. Why? A denial would be a renunciation of such a claim. If it's just Judas accusing him and only Jesus is arrested, Jesus' word should carry well against that of Judas. That brings up another problem I have with this whole scenario. According to Josephus, when the Romans attacked Theudas, they killed or captured most of his followers. Yet, we are supposed to believe that only Jesus is taken, leaving Peter and the others free. Yet, they would have been Jesus' co-conspirators.