"And Jesus answering them began to say, Take heed lest any man deceive you: For many shall come in My name, saying, I am Christ; and shall deceive many" (Mk. 13:5-6).
"And He said, Take heed that ye be not deceived: for many shall come in My name, saying, I am Christ; and the time draweth near: go ye not therefore after them" (Lk. 21:8).
"I am come in My Father's name, and ye receive Me not: if another shall come in his own name, him ye will receive" (Jn. 5:43).
Whenever I have heard these verses preached, and in the Bible Commentaries I have consulted, these verses are always interpreted as saying: "Do not believe any man who comes saying to you that he is Christ." And, technically, I have absolutely no reason to deny that interpretation as being correct. The Bible clearly teaches that the Antichrist will come and deceive many (1 Jn. 2:18; 2:22; 4:3; 2 Jn. 1:7). The four references to the Antichrist tell us that this individual will deny Jesus was the Christ (1 Jn. 2:22), he will deny that God has a Son (1 Jn. 2:22), and he will even deny that Jesus existed in the flesh (1 Jn. 4:3; 2 Jn. 1:7)! In other words, he will say he is the one about whom the prophecies foretold.
But, I believe there is another interpretation that, although it may not be the correct one, it will also be true. The Bible tells us that there will be "wolves in sheep's clothing" who will pretend to be Christians, but will be false teachers (Mt. 7:15; Acts 20:29; 2 Pet. 2:1; etc.). These men will preach the truth about the Lord's First Advent, and some will even include the Gospel message that says Jesus died for our sins, that He was buried, and that God raised Him from the dead (1 Cor. 15:3-4). The problem is, they will also tell you that you must obey the Law, avoiding sin and doing good works, in order to be "saved" and to "stay saved" (Gal. 1:1-9; 2:16; 3:1-5; etc.)! The may even fool themselves, believing their own works, and their having acknowledged Jesus as their Lord, qualifies them to go to heaven (Mt. 7:21-23)! Salvation is a gift, period (Eph. 2:1-8)!
Claiming to be Jesus, or denying Him, has the very same result: the Lake of Fire!