Which will prepare the way before thee
The purpose of the forerunner is to prepare the 'way' of the Lord. This suggests that the one following is the Lord. Isaiah speaks in 3rd person of the Lord coming. But the prophecy of Malachi above is spoken by the Lord in first person; "He shall prepare the way before ME."
The way
There are two words closely related in Hebrew:
Way 02015 הפך haphak - turn back, overthrow
Path 0734 ארח ‘orach - Highway
The way is the way back. Jesus said he was the way, [1]
Consider then that John was doing something to prepare the way back for Jesus. He had left his high estate as God of very God, and was found in the form of a man. [2]