I view the moral argument for God as the most powerful apologetic argument. William Lane Craig agrees although his favorite argument is the Kalam Cosmological Argument. Soon, I will soon post my version of the moral argument, asserting that an objective, transcendent source for morality must exist or moral chaos results. In the meantime, Noel Vincent posted an interesting essay here in 2014 exploring the perspective of CS Lewis on the moral argument. Vincent writes,

The relativist is quick to deny a common moral standard. But, relativists often appeal to that very standard when making moral judgments of their own, yet they do not always see that they hold contradictory views, one the one hand that no moral standard exists, and on the other hand that others should agree with their assessment of what is a moral wrong.  If there is no standard of morality, then each relativist is free to decide arbitrarily what is and is not morally wrong. . . . . Everyone makes moral judgments.  A judgment implies a standard for judging questions and issues of morality.  A standard implies an author and arbiter of the standard.  The author and arbiter is separate and distinct from human beings and must transcend time and space.  The logical conclusion is the concept of God.