If you look at the whole life of John the Baptist he has three different reactions to his experience of Jesus at three different times.  The first reaction comes while he is still in the womb.  He leaps for joy when Mary (carrying unborn Jesus) walks into the room.  The second reaction comes when he and Jesus are about 30.  Jesus comes to be baptized and John responds with humility: “I’m unworthy to baptize you.”  The third time comes right at the end of life.  He doubts.  John seems to question who Jesus is and what he is up to. This man who had previously been so sure now needs a “firsthand refresher.”  The refreshment comes in the context of Jesus word.  He points backwards to what the prophets said and points to the present to what’s happening.