Was Jesus the founder of Christianity?

Most Christians will respond emphatically that Jesus is the founder of Christianity just like Mohammed is the founder of Islam. Was he?

The following is, in brief, the view of James Tabor: [emphasis mine]

James Tabor

“Jesus, as we know, was the son of Mary, a young woman who became pregnant before her marriage to a man named Joseph.  The gospels tell us that Jesus had four brothers and two sisters, all of whom probably had a different father from him.  He joined a messianic movement begun by his relative John the Baptizer, whom he regarded as his teacher and as a great prophet.  John and Jesus together filled the roles of the Two Messiahs who were expected at the time, John as a priestly descendant of Aaron and Jesus as a royal descendant of David. Together they preached the coming of the Kingdom of God.  Theirs was an apocalyptic movement that expected God to establish his kingdom on earth, as described by the prophets.  The two messiahs lived in a time of turmoil as the historical land of Israel was dominated by the powerful Roman Empire.  Fierce Jewish rebellions against Rome occurred during Jesus's lifetime.

John and Jesus preached adherence to the Torah, or the Jewish Law.  But their mission was changed dramatically when John was arrested and then killed.  After a period of uncertainty, Jesus began preaching anew in Galilee and challenged the Roman authorities and their Jewish collaborators in Jerusalem.  He appointed a Council of Twelve to rule over the twelve tribes of Israel, among whom he included his four brothers.  After he was crucified by the Romans, his brother James – the “Beloved Disciple” – took over leadership of the Jesus Dynasty. 

James, like John and Jesus before him, saw himself as a faithful Jew.  None of them believed that their movement was a new religion.  It was Paul who transformed Jesus and his message through his ministry to the gentiles, breaking with James and the followers of Jesus in Jerusalem, preaching a message based on his own revelations that would become Christianity.  Jesus became a figure whose humanity was obscured; John became merely a forerunner of Jesus; and James and the others were all but forgotten.”

Who is this Paul Tabor is referring to?