Skeptics and critics have claimed the gospels contradict about whether King Herod thought Jesus was John the Baptist. 

Alleged contradiction:

Did Herod think that Jesus was John the Baptist?
(a) Yes (Matthew 14:2; Mark 6:16)
(b) No (Luke 9:9)

Let’s first look at what Herod was afraid of:

“When Herod Antipas, the ruler of Galilee, heard about Jesus, he said to his advisers, “This must be John the Baptist raised from the dead! That is why he can do such miracles.”—Matthew 14:1,2 NLT

Since Jesus was already famous for doing miracles, Herod’s guilty conscience bothered him so much that he was fearful John the Baptist might have been resurrected by God.

“Now Herod the tetrarch heard about all that was happening, and he was perplexed, because it was said by some that Elijah had appeared, and by others that one of the prophets of old had risen. Herod said, ‘I beheaded John, but who is this about whom I hear such things?’ And he sought to see him'”—Luke 9:9 ESV

But technically, Luke 9:9 does not supply the claim “Jesus is not John the Baptist” that is necessary to make this a case of “Bible contradiction.”  A careful look at Luke 9:9 reveal that Herod was asking a question, “but who is this, of whom I hear such things?”

 To be precise, the question indicated that Herod was wondering who Jesus was; it was not a denial of the possibility that Jesus was John the Baptist.  Herod was confused; this is indicated by the fact that in Luke 9:9 it states that “he was perplexed,” Herod’s use of the interrogative pronoun in the Greek to show him asking a question since the people have all kinds of speculations about Jesus and finally, Herod being curious, “desired to see him,” as the end of the verse said.  Wondering about the identity about Jesus is not a denial of Herod’s thinking Jesus was John the Baptist