Everyone seems to have an agenda. I admit that I think that someone named Mark founded one of the largest organized movements within the early family of Christian sects. He was probably the most successful of the successors to Jesus in earliest Christianity.
When I come across Jerome effectively a lost testimony of Origen that the Marcionites had the following words at the beginning of the Letter to the Galatians (which many feel was the first epistle following the gospel in the canon):
παυλος αποστολος ουκ απ ανθρωπων ουδε δι ανθρωπου αλλα δια ιησου χριστου του εγειραντος αυτον εκ νεκρων
Paul, an apostle, not from men, neither by man, but by Jesus Christ, who raised him from the dead
This superscription - like all New Testament superscriptions - was written by someone other than the original author of the text (an editor). When I read this I know that my theories about Secret Mark can't be completely off-base. You see the rest of scholarship just says that the Marcionites 'took out' the phrase 'through the Father' without actually looking at how the 'subtraction' transforms the rest of the sentence.
Indeed when you take 'the Father' out of the last half of the sentence it can't be Jesus who was raised from the dead. Just look at the way 'the Father' was thought to modify 'Jesus' in the last sentence:
Paul, an apostle (not sent from men nor through the agency of man, but through Jesus Christ and God the Father, who raised Him from the dead
To this end, most people reason that Paul is saying that he was an apostle of Jesus that guy who was raised from the dead by the Father. If you take out the 'by God the Father' (as the Marcionites did) the simple-minded are left to conclude that Paul is saying that he is the apostle for that guy Jesus who raised himself from the dead. Yet when you really look at corrected text of Tertullian it is plain that this was not the original sense of the Marcionite interpretation. Instead we find the Marcionites seem to have intimated that Paul was the Christ and Jesus, God.
For the earliest strata of material preserved by Tertullian clearly implies that the original author - a Syrian author who may well have used Justin's gospel and perhaps denied the authority of 'Paul' - seems to equate the apostle with claiming that he, rather than Jesus, was the real messiah:
I require to know of Marcion the origin of his apostle even— I, who am to some degree a new disciple, the follower of no other master; who at the same time can believe nothing, except that nothing ought to be believed hastily (and that I may further say is hastily believed, which is believed without any examination of its beginning); in short, I who have the best reason possible for bringing this inquiry to a most careful solution, since a man is affirmed to me to be an apostle whom I do not find mentioned in the Gospel in the catalogue of the apostles. Indeed, when I hear that this man was chosen by the Lord after He had attained His rest in heaven, I feel that a kind of improvidence is imputable to Christ, for not knowing before that this man was necessary to Him; and because He thought that he must be added to the apostolic body in the way of a fortuitous encounter rather than a deliberate selection; by necessity (so to speak), and not voluntary choice, although the members of the apostolate had been duly ordained, and were now dismissed to their several missions. Wherefore, O shipmaster of Pontus, if you have never taken on board your small craft any contraband goods or smuggler's cargo, if you have never thrown overboard or tampered with a freight, you are still more careful and conscientious, I doubt not, in divine things; and so I should be glad if you would inform us under what bill of lading you admitted the Apostle Paul on board, who ticketed him, what owner forwarded him, who handed him to you, that so you may land him without any misgiving, lest he should turn out to belong to him, who can substantiate his claim to him by producing all his apostolic writings. He professes himself to be an apostle— to use his own, words— not of men, nor by man, but by Jesus Christ. Of course, any one may make a profession concerning himself; but his profession is only rendered valid by the authority of a second person. One man signs, another countersigns; one man appends his seal, another registers in the public records. No one is at once a proposer and a seconder to himself. Besides, you have read, no doubt, that many shall come, saying, I am Christ. [Against Marcion 1:1]
We have already seen the same formula is preserved among the early Coptic Church Fathers with respect to St. Mark - namely that he was the Christ heralded by Jesus.
I can't believe that people would really believe that Marcion interpreted the first line of Galatians as if Jesus was both man (i.e. Christ) and God when Jerome tells exactly the opposite in his discussion. In other words, the Marcionites only thought Jesus was God. As such someone else necessarily must have been the Christ. The logical choice of course is Paul - i.e. the apostle - given that we have a document from Osroene (i.e. the Acts of Archelaus which makes explicit the knowledge that the Marcionites thought Paul was the Paraclete - a fact which is already witnessed by Origen's Commentary on Luke.
It takes a massive amount of cultivated ignorance not to recognize that 'Paraclete' is a title of the messiah. Almost every page of the Acts of Archelaus makes reference to the doctrine of 'Paul the Paraclete.' Notice at once that when Mani comes forward to claim this title for himself that the Marcionite community of Osroene goes to great lengths to reestablish Paul in his traditional role:
And wherein, forsooth, did He make any tarrying, so that we should have to believe Him to have waited so long, even to these days, before He actually sent the Paraclete? Nay, rather, as has been already said above, He gave proof of His presence with us immediately, and did most abundantly impart Himself to Paul, whose testimony we also believe when he says, Unto me only is this grace given. For this is he who formerly was a persecutor of the Church of God, but who afterwards appeared openly before all men as a faithful minister of the Paraclete; by whose instrumentality His singular clemency was made known to all men, in such wise that even to us who some time were without hope the largess of His gifts has come. For which of us could have hoped that Paul, the persecutor and enemy of the Church, would prove its defender and guardian? Yea, and not that alone, but that he would become also its ruler, the founder and architect of the churches? Wherefore after him, and after those who were with Himself— that is, the disciples— we are not to look for the advent of any other (such), according to the Scriptures; for our Lord Jesus Christ says of this Paraclete, He shall receive of mine. Him therefore He selected as an acceptable vessel; and He sent this Paul to us in the Spirit. Into him the Spirit was poured; and as that Spirit could not abide upon all men, but only on Him who was born of Mary the mother of God, so that Spirit, the Paraclete, could not come into any other, but could only come upon the apostles and the sainted Paul. For he is a chosen vessel, He says, unto me, to bear my name before kings and the Gentiles. The apostle himself, too, states the same thing in his first epistle, where he says: According to the grace that is given to me of God, that I should be the minister of Jesus Christ to the Gentiles, ministering the Gospel of God. I say the truth in Christ, I lie not, my conscience also bearing me witness in the Holy Ghost. And again: For I will not dare to speak of any of those things which Christ has not wrought by me by word and deed. I am the last of all the apostles, that am not meet to be called an apostle. But by the grace of God I am what I am. And it, is his wish to have to deal with those who sought the proof of that Christ who spoke in him, for this reason, that the Paraclete was in him: and as having obtained His gift of grace, and as being enriched with magnificent, honour, he says: For this thing I besought the Lord thrice, that it might depart from me. And He said unto me, My grace is sufficient for you; for strength is made perfect in weakness. Again, that it was the Paraclete Himself who was in Paul, is indicated by our Lord Jesus Christ in the Gospel, when He says: If you love me, keep my commandments. And I will pray my Father, and He shall give you another Comforter. In these words He points to the Paraclete Himself, for He speaks of another Comforter. And hence we have given credit to Paul, and have hearkened to him when he says, Or do you seek a proof of Christ speaking in me? and when he expresses himself in similar terms, of which we have already spoken above. Thus, too, he seals his testament for us as for his faithful heirs, and like a father he addresses us in these words in his Epistle to the Corintians: I delivered unto you first of all that which I also received, how that Christ died for our sins according to the Scriptures; and that He was buried, and that He rose again the third day according to the Scriptures; and that He was seen of Cephas, then of the eleven apostles: after that He was seen of above five hundred brethren at once; of whom the greater part remain unto this present, but some are fallen asleep. After that He was seen of James; then of all the apostles. And last of all He was seen of me also, as of one born out of due time. For I am the last of the apostles. Therefore, whether it were I or they, so we preach, and so you believed. And again, in delivering over to his heirs that inheritance which he gained first himself, he says: But I fear, lest by any means, as the serpent beguiled Eve through his subtlety, so your minds should be corrupted from the simplicity that is in Christ. For if he that comes preaches another Christ, whom we have not preached, or if you receive another Spirit, which we have not received, or another gospel, which you have not accepted, you might well bear with him. For I suppose that I did nothing less for you than the other apostles.
These things, moreover. he has said with the view of showing us that all others who may come after him will be false apostles, deceitful workers, transforming themselves into the apostles of Christ. And no marvel; for Satan himself is transformed, like an angel of light. What great thing therefore is it, if his ministers also be transformed into the ministers of righteousness?— whose end shall be according to their works. He indicates, further, what manner of men these were, and points out by whom they were being circumvented. And when the Galatians are minded to turn away from the Gospel, he says to them: I marvel that you are so soon removed from Him that called you unto another gospel: which is not another; but there be some that trouble you, and would turn you away from the Gospel of Christ. But though we, or an angel from heaven, preach any other gospel unto you than that which has been delivered to you, let him be accursed. And again he says: To me, who am the least of all the apostles, is this grace given; and, I fill up that which was behind of the afflictions of Christ in my flesh. And once more, in another place, he declares of himself that he was a minister of Christ more than all others, as though after him none other was to be looked for at all; for he enjoins that not even an angel from heaven is thus to be received. And how, then, shall we credit the professions of this Manes, who comes from Persis, and declares himself to be the Paraclete? By this very thing, indeed, I rather recognise in him one of those men who transform themselves, and of whom the Apostle Paul, that elect vessel, has given us very clear indication when he says: Now in the last times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils; speaking lies in hypocrisy; having their conscience seared with a hot iron; for-bidding to marry, and commanding to abstain from meats, which God has created to be received with thanksgiving of them which believe and know the truth. For every creature of God is good, and nothing to be refused, if it be received with thanksgiving. The Spirit in the evangelist Matthew is also careful to give note of these words of our Lord Jesus Christ: Take heed that no man deceive you: for many shall come in my name, saying, I am Christ; and shall deceive many. But if any man shall say unto you, Lo, here is Christ, or there; believe it not. For there shall arise false Christs, and false apostles, and false prophets, and shall show great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect. Behold, I have told you before. If they shall say unto you, Behold, he is in the desert; go not forth: if they shall say, Behold, he is in the secret chambers; believe it not. And yet, after all these directions, this man, who has neither sign nor portent of any kind to show, who has no affinity to exhibit, who never even had a place among the number of the disciples, who never was a follower of our departed Lord, in whose inheritance we rejoice—this man, I say, although he never stood by our Lord in His weakness, and although he never came forward as a witness of His testament, yea rather, although he never came even within the acquaintance of those who ministered to Him in His sickness, and, in fine, although he obtains the testimony of no person whatsoever, desires us to believe this profession which he makes of being the Paraclete; whereas, even were you to do signs and wonders, we would still have to reckon you a false Christ, and a false prophet, according to the Scriptures. [Acts of Archelaus 34, 35]
The point is that all the pieces are there for (a) the Marcionites holding their apostle to have been the Christ and (b) for interpreting Paul to have been the 'Christ' who was raised from the dead by Jesus. The fact that 'Secret Mark' already has us there is just a bonus.