That would be the mild-mannered, sweet-tempered legal and moral theorist Robert George of Princeton. (See his books here.) He is the subject of a lengthy profile by David Kirkpatrick, formerly the NY Times resident anthropologist of conservatives. The key to being "this country's most influential conservative Christian thinker" lies in his advocacy of natural law, though a natural law rooted in analytic philosophy, not Thomism or Aristotle. Thus, Kantian practical reason (not Scriptural interpretation) becomes the basis for the defense of life against abortion, for decency against pornography, and for chastity against promiscuity. Kirkpatrick's focus on sexuality distorts George's approach--one of the most touching of George's essays concerns the gratitude immigrants owe this country.
In this regard, George's Kantianism resembles that of Hadley Arkes, who is however an overt follower of Leo Strauss. It might be contrasted with the Thomism of James V. Schall, of Advent Conversations fame. But all of these conservatives wind up politically in the same place.
It is unavoidable to note a certain a-political quality of the George approach, one that makes it alluring to Princeton undergraduates and acceptable to his colleagues. (He co-teaches a class with Cornel West.) Contrast George with Harry V. Jaffa, doubtless the profoundest thinker of American conservatism and also one tough brawler--still writing, now on Leo Strauss, at age 91: William F. Buckley, Jr., once remarked that as hard as it is to disagree with Harry Jaffa, it's even harder to agree with him.
H/T WheatandWeeds "Pass the Biscuits."