John was aware of Jesus but was clearly expecting more than one person - “Are You the Expected One, or do we look for someone else?”
Messiah was used arguably loosely and could indicate – anointed one, messenger, Prophet a person chosen by God – so Messiah is not inclusively Jesus, but generally relates to Jesus.
Was someone else expected few references from NT only with much more in the OT.
Luke 3:16 16 John answered them all, “I baptize you with water. But one who is more powerful than I will come, the straps of whose sandals I am not worthy to untie. He will baptize you with the Holy Spirit and fire. (will come – Jesus was already here)
Mark 1:7 7 And this was his message: “After me comes the one more powerful than I, the straps of whose sandals I am not worthy to stoop down and untie.
John 1:19-27 19 Now this was John’s testimony when the Jewish leaders in Jerusalem sent priests and Levites to ask him who he was. 20 He did not fail to confess, but confessed freely, “I am not the Messiah.” (note this would be Jesus) 21 They asked him, “Then who are you? Are you Elijah?” He said, “I am not.” “Are you the Prophet?” (so who is that prophet)
John 15:26 - 26 “When the Advocate comes, whom I will send to you from the Father—the Spirit of truth who goes out from the Father—he will testify about me. (Jesus is talking about sending someone, clearly not him and not holy spirit (HS is truth, guidance strength etc…) also HS has been there since beginning and continuously in the bible)
John 16:7-8 7 But very truly I tell you, it is for your good that I am going away. Unless I go away, the Advocate will not come to you; but if I go, I will send him to you. 8 When he comes, he will prove the world to be in the wrong about sin and righteousness and judgment:
John 16:13 13 But when he, the Spirit of truth, comes, he will guide you into all the truth. He will not speak on his own; he will speak only what he hears, and he will tell you what is yet to come.
John 14:16 16 And I will ask the Father, and he will give you ***another ***advocate to help you and be with you forever (another / new not HS already hear or a person already hear)
John 14:30-31 30 I will not say much more to you, for the prince of this world is coming. He has no hold over me, 31 but he comes so that the world may learn that I love the Father and do exactly what my Father has commanded me. (someone coming not here already)
John 14:26 26 But the Advocate, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you.
Acts 3:22 - 22 For Moses truly said to the fathers, ‘The LORD your God will raise up for you a Prophet like me from your brethren, Him you shall hear in all things, whatever He says to you.