This means, *Ev knows John and knows that he was a baptizer. [The information is found also in Jos., Ant. XVIII 116-119] All further information about him is missing in*Ev and inserted in later stages of the tradition history. From the brief comment about the execution by Herod, pre-canonical *Mark extricated his detention (Mark 6,17 || Matt 4,12 || Luke 3,19f) as well as the account of his execution urged by Herodias (Mark 6,18-29). Belonging to the successive tradition since *Mark is above all: Jesus' baptism by John; John's repentance sermon; his proclamation of the one who is 'more powerful' coming after him to baptize with fire and the spirit; the identification of John with Elijah; and the existence of John's disciples in the apostolic time. In that successive attribution, the ambivalence of Jesus' judgment of John the baptist is still preserved. Mark adopted the proclamation of the 'more powerful' into the account of the baptism activity (Mark 1,7f || Matt 3,11). Matthew, furthermore, integrated Jesus' superiority into the baptism account through John the Baptist's refusal to baptize Jesus (Matt 3,14f). John pointedly expressed the differentiated judgment of the activity thorugh characterizing John as a witness who 'testifies to the light', but who himself 'was not the light' (John 1,7f). Luke, finally, gives this differentiated characterization the broadest expanse thorugh harmonizing the birth accounts (Luke 1f) and thorugh the meeting of Elizabeth and Mary (Luke 1,36-45). The baptism account of John's disciples in Ephesus (Acts 19,2-7) exemplifies that the superiority of Jesus over John, or of the Christians over John's disciples, is rooted in the baptism's various effects.
(The Oldest Gospel and the Formation of the Canonical Gospels, p. 368, my bold, original cursive)
In my view, the entire price of the book is found in this page, but surely I am an idiot in ignoring the rest.
Note how Klinghardt finds a trace of the earliest rivalry survived in Mark 1:7: