Was Constantine The Great a Nicene Christian? Lately I've been trying to figure out whether or not Constantine is a Nicene Christian. He was baptised by Eusebius who was of course an Arian. And since he was very close to Eusebius, he was influenced by Arian views (exiling Saint Athanasius). Some sources I have looked at say that he favored Arianism instead of the Orthodox christian view. Others say that he also exiled Eusebius because he continued to teach Arianism. Was Constantine an Orthodox/Nicene Christian believing Christ was in fact God?
This answer is based on the following 3 resources I found:


A 2015 article Was Constantine the Great Baptized An Arian?
A 2012 paper The Spread Out of Arianism.  A Critical Analysis of the Arian Heresy published in the International Journal of Orthodox Theology
A 2005 article How Arianism Almost Won by Christopher A. Hall published in Christian History Issue #85


There was quite an upheaval between the Council of Nicaea (AD 325) and Constantine's baptism shortly before his death (AD 337) by an Arian sympathizer bishop Eusebius of Nicomedia. But although Eusebius tried to bring back Arianism, he DID sign the creed, making him an Orthodox bishop.  Initially after Nicaea Constantine was strongly opposed to Arianism, ordering Arius's works to be burned.  But,


  [w]ithin ten years of the Council of Nicaea, though, Constantine became convinced that Arius’s ideas fell within the pale of orthodoxy, though the exact details of Arius’s position — at least as represented to the emperor in the years following Nicaea — remain somewhat murky.   What is clear, though, is that neither Constantine nor later sons such as Constans and Constantius were skilled biblical interpreters or theologians. These Roman emperors were more concemed to preserve the unity of the church than to engage in prolonged debates over what to them often seemed theological nitpicking. [...skipped...] Both Arius and Athanasius experienced Constantine’s displeasure. It was Constantine who in A.D. 335 ordered the first of Athanasius’s five exiles—the same year Arius regained the favor of the Roman emperor.  [from "How Arianism Almost Won"]


The resurgence of Arianism was fought in earnest only after Constantine's death, but then suffered a definitive defeat at the Council of Constantinople 56 years after Nicaea.

Therefore, it appears that since Constantine was not a theologian, he was under the impression that he believed the orthodox faith.


  ... as far as Constantine knew, Eusebius repented of his error in his letter and he was restored to his See and gained the favor of Constantine precisely because he was Orthodox. And it was from this canonical bishop of the Orthodox Church, Eusebius of Nicomedia, that Constantine received Holy Baptism, fully in canonical communion with the Church. Consequently, there is no hesitation on the part of the Orthodox Church, which takes the entire historical data into account, that Constantine the Great was baptized as an Orthodox Christian by an Orthodox bishop.  [from "Was Constantine the Great Baptized an Arian"]