Who was John the Baptist?
In the New Testament layers of tradition overlay accounts of John the Baptist. J.K. Elliott describes how these accounts were imposed by writers who altered historical details to suit their own doctrinal ends.
If John the Baptist had attracted better propagandists, the religious movement he founded could have rivalled Christianity - and even overtaken it in popularity. Just how popular John was is not always obvious from the New Testament. That is because the writers of the Christian scriptures altered the historical details about John to suit their own ends.
With the exception of a few references to John in one or two non-Christian documents, we are really dependent on the New Testament for historical evidence about John the Baptist and his movement. But because of the theological bias of the New Testament we cannot accept its evidence uncritically.
When looking behind the finished gospels, one has to peel away the layers of tradition underlying them - especially if one is trying to expose their historical kernel. In the case of the traditions surrounding John the Baptist, the reader needs to appreciate that there are at least four layers.