My thought is that Constantine is not as problematic a figure as the Anabaptistic (though not exclusive or originating with them) account of the Fall of the Church. The reading goes as such: The Church existed in peace as a non-state, or even antagonistic to the State, entity until Constantine suckered the Church with the Edict of Milan (313), where the Empire's government would no longer persecute Christians. This was followed by Constantine's slow ingratiation into the Church, convening councils (most notably Nicaea), enforcing doctrinal decisions, and pouring money and prestige into the Church (there was a sweeping building campaign, and Eusebius of Caesarea had influential places in the court). From there, the Church spiraled into a place of dual compromise, either existing Erastianly (as an organ of the State) or Caesaropapally (Church absorbing the role of the State, or controlling the engines of government). This was the deathblow that drove discerning Christians underground.
I don't believe in this story, though I am sympathetic to the major themes involved. Power, as the World holds and defines it, is corrupt and corrupting. Confusing the Church with a political program is bad and destructive for the Church, even if it can buy benefits in the short run. Erastianism and Caesaropapalism are sinful heresies. However, I do not believe Constantine is the problem.
Peter Leithart wrote a book called "Defending Constantine" which attempted to rebut John Howard Yoder's mainstream defense of the Anabaptist narrative. It's a stupid premise. Leithart's book completely missed the point and wasted time actually trying to defend Constantine the individual. That was not Yoder's point. And it's not my point either.
Constantine was not the problem. In fact, his reign was probably one of the most just in the entirety of Roman history. This is considering how much power the Roman emperor could exercise at this point. He was not the restrained dictator of the Julio-Claudians or the rule of the five wise emperors (Nerva, Trajan, Hadrian, Antoninus Pius, Marcus Aurelius). He was, as they say, an oriental despot, possessing full control and fully able to basque in his own cult (Diocletian portrayed himself as Zeus in the flesh).
I am not vindicating all of what Constantine did. He misunderstood Christ's commands, and he should have been much more skeptical of wearing the purple. He ought to have left Pagans keep their temples and not harass them. This is more shameful considering he used money to build houses of worship for the Church on top of bulldozed temples.
However, I am joyful that Constantine ended the persecution. I don't mind that he convened ecclessial councils, even though he contaminated some of the decisions with imperial concerns. However, contrary to the mythologizing of Nicaea, the council was not considered much of a success by most bishops attending. Most went home without a second thought. Constantine, here, was not the problem.
However, the problem is when Constantine is turned into a symbol. The historical contingency surrounding Constantine's reign is unique and belongs to its era, and its era alone. The problem is when Constantine becomes a systemic program, where the Church seeks to control the levers of power. It's when a Christian emperor becomes a Christian empire. This was Yoder's main concern.
This is when the Church becomes wed to a particular politics, abandons its Heavenly commissioning, and becomes a Satanic institution. I have little problem with Eusebius' statement that God brought Constantine to the throne in order to vindicate the Church from persecution. But a reflection on God's care is not the same as a forward looking constructive approach. This is the sin of Constantinianism, that Constantine unfortunately represents.
Unlike Tertullian, Yoder believed that princes, or high political figures, could indeed be saved. He was just unsure whether this had occurred yet. I think Constantine actually qualifies under this header. I've read that he was a genuine, though confused, Christian, I have also read that he was a cynical manipulator. I don't know. But we can't blame Constantine, or even the almost obsequious Eusebius for what would later become written into the constitution of the Roman Empire, and build the vile beast that was/is Christendom. The Church ought to have awakened to the provisional nature of this arrangement when the following emperor was an avid Arian, and brought persecution upon the orthodox.
Fast forwarding, another fascinating figure is the Count Nicholas Ludwig von Zinzendorf. He was a nobility of the Holy Roman Empire who became a devout Christian. He turned his estate into a home for the persecuted Unity of Brothers (who would become known as the Moravians). He studied theology, he abandoned most of his princely prerogatives, and took to becoming an avid proponent of missions. He even helped form Bethlehem (Pennsylvania), a Christian commune that abolished poverty and maintained social harmony without a cultic apparatus. He was a deeply profound theologian of his time and is oft neglected in the history of Christianity.
Zinzendorf had his own sins. His commanding personality overwhelmed the functioning of the Church. His own royal upbringing blinded him from certain realities that were all too present to the mostly peasant/worker base that formed the Unity. As extreme as he was in his own milieu, he conformed to some of the deepest prejudices of his day (colonialism/slavery/European cultural form confused with Christianity proper). Yet, despite this, he is a prince who was saved.
Unlike Constantine, Zinzendorf was so eccentric and abnormal for his time and place that he was never replaced. Anti-Constantinianism was woven into the Unity's bones, from its time back in the Hussite revolt. However, both Constantine and Zinzendorf open up a window of possibility that God may indeed be convert even princes to his own. I'd count both of them saints.
All of this might come as a shock for those who've been reading me or know me. But this is not much of a change. I am just simply less ideological about God's working and presence. I thank God for St. Constantine, even if his legacy is (and continues to be) a veil of tears.