This song is full of biblical allusions, but its ultimate meaning is murky. At times it seems to be Dylan speaking as Jesus, the "real prophet," but at other times he seems to be speaking as the "false prophet." Ultimately, the song's title is the best indication as to the real meaning. Though at times Dylan speaks very convincing words as a true prophet, the character in this song is ultimately not the real deal.
False prophets appear multiple times in the Bible but are especially important in the story of Jesus related in the New Testament. In Matthew 24:23-24, for example, Jesus states (in what is frequently referred to as the "Little Apocalypse"):
Then if anyone says to you, 'Behold, here is the Christ,' or, 'There He is,' do not believe him. For false Christs and false prophets will arise and will show great signs and wonders, so as to mislead, if possible, even the elect.
This idea comes back in the final book of the Bible, the Book of Revelation, also called the Apocalypse of John. In that story, the false prophet ushers in the coming of the Beast. He appears to be good and Christly but is really a bringer of doom that is eventually cast into a lake of fire and brimstone. This is probably who Dylan is referring to, seeing as how the figure was prophesied to appear in the future of the early Christians, which would include today.