Whither A Christian Political Realism?

The political thought of two theologians, the Catholic, John Courtney Murray, and the Protestant, Reinhold Niebuhr, can be reconciled and contrasted with more idealist, absolutist, fundamentalist approaches.

This is because a shared moral realism and ethical naturalism will be transparent to human reason prior to any putative special religious revelations. They are best combined with a pragmatic, political realism, which practices the art of the possible.

Realism, as in moral realism, refers to a metaphysical stance, asserting an objective basis to morality.
Naturalism, as in ethical naturalism, refers to an epistemic approach, asserting that our natural sciences (not religious or ideological dogma) should guide our ethical norms to optimally realize moral truths, albeit fallibly. Mortimer Adler’s Common Sense approach to moral & political philosophy shows how humanity shares evaluative dispositions and moral prescriptions regarding the most general precepts.
Realism, as in political realism, refers to —neither a metaphysical (what is) nor epistemological (how we know what is) reality, but — to any practical realization regarding what’s achievable, recognizing value in what’s suboptimal, eschewing any tendency to let the best become the enemy of the good.
Taken together, these moral, ethical and political stances can be reconciled with both secular and religious humanisms. When supplemented by the vocational and relational norms of the Gospel, one can, in my view, best practice a Christian realism, politically. Its default bias would necessarily be conservative and libertarian (in the classical liberal sense and not as malpracticed by many currently).
For yet another attempt at reconciliation between these theologians, I commend:

John Courtney Murray and Reinhold Niebuhr: Natural Law and Christian Realism
Journal of Catholic Social Thought, Vol. 3, 2006
U of St. Thomas Legal Studies Research Paper No. 05-20
21 Pages
Thomas C. Berg
University of St. Thomas, St. Paul/Minneapolis, MN – School of Law