In the wake of the 'revisionist history' nonsense about Constantine being the great establisher of Christian orthodoxy and suppressor of heterodoxy (which it is a stretch to even call a half truth), it is refreshing to read the works of scholars who actually know the primary sources when it comes to Constantine.
One such person is Edwin Judge, the fine social historian, now retired from MacQuarrie University in Sydney Austrailia. I have been working through the papyri of the early Christian era with the help of "New Documents which Illustrate Early Christianity" These volumes are invaluable, and Judge was a regularly contributor to them in the early days of the serial (which now has thankfully been picked up and published by Eerdmans).
The inscription I am interested in was found not in the east (e.g. Asia Minor), where Emperors were more frequently worshipped, but in Umbria no less in Italy itself. Its date is 336 A.D. in the very midst of Constantine's reign and well after he declared his allegiance to Christianity, at least nominally, and removed the Christian faith from the list of 'superstitio' ending the Christian persecutions which had reaced new heights under Diocletian. The inscription in question reads "The council of Plestia to the deified Flavius Valerius Constantinus Augustus".
Judge (New Docs II, p. 192) commenting says that this inscription "pinpoints the fact that the establishment of Christendom had by no means done away with the Imperial cult; rather it had clarified some of its ambiguities. The Caesars had mostly insisted on their own humanity, at the same time as they accepted or encouraged the cult as an expression of gratitude and loyalty....The conversion of Constantine helped define the difference [between Emperors who made explicit claims to deity like Gaius, and Emperors like Constantine who saw it as a sort of hyperbolic loyalty statement]. He promoted his own family's temple and cult 'provided it is not polluted by the deceits of any contagious superstition.' But as one chosen by God he could both revive traditional disclaimers of divinity and anticipate his own apotheosis in the form of a personal reception into heaven at death.... Paradoxically the Christianization of the [Emperor] cult may actually have open the way for people seriously to pray to their rulers for the first time. Their divine calling and sanctity ranked them with the saints in this respect....."
Thus far Edwin Judge. I would add that when we closely examine the historical records about Constantine, we discover that he continued to be a patron of various pagan priests and cults until his death. Here is an excerpt from the Catholic Encyclopedia (online) on Constantine:
"In the dedication of Constantinople in 330 a ceremonial half pagan, half Christian was used. The chariot of the sun-god was set in the market-place, and over its head was placed the Cross of Christ, while the Kyrie Eleison was sung. Shortly before his death Constantine confirmed the privileges of the priests of the ancient gods. Many other actions of his have also the appearance of half-measures, as if he himself had wavered and had always held in reality to some form of syncretistic religion. Thus he commanded the heathen troops to make use of a prayer in which any monotheist could join, and which ran thus: "We acknowledge thee alone as god and king, we call upon thee as our helper. From thee have we received the victory, by thee have we overcome the foe. To thee we owe that good which we have received up to now, from thee do we hope for it in the future. To thee we offer our entreaties and implore thee that thou wilt preserve to us our emperor Constantine and his god-fearing sons for many years uninjured and victorious." The emperor went at least one step further when he withdrew his statue from the pagan temples, forbade the repair of temples that had fallen into decay, and suppressed offensive forms of worship. But these measures did not go beyond the syncretistic tendency which Constantine had shown for a long time. Yet he must have perceived more and more clearly that syncretism was impossible."
What this all makes abundantly clear is that while Constantine's conversion may have been real, nonetheless he was a shrewd politician who did not simply repudiate the practices of Rome's past, but rather operated in a pluralistic fashion. The manner in which he helped Christianity was by taking it off the list of superstitions or banned religions. He certainly did not impose orthodoxy on the Empire or draw and quarter all the Gnostics nor eliminate their texts. Sorry Dan Brown, Elaine Pagels, Karen King, Marvin Meyer. It will not do to paint Constantine as the watershed, or big bad guy who supressed your texts of interest.