Luke 3:15

Many reasons might have induced the people to think that John was the Christ: 1. The wonders that took place at his birth and conception, his mother being very old, and without any prospect of offspring: 2. the excellence of his preaching, his mortified life, and the novelty of his baptism; and thirdly, the report which them generally prevailed among the Jews, that the Messias was already come; on account of the coming of the magi, and the murder of the infants by Herod: both which circumstances were probably fresh in their memory; and several perhaps, who witnessed them, were still living. (Denis the Carthusian)