How rhetorical ability comes about has been an area of attention in rhetoric from the beginning. In De oratore, Cicero's characters debate which of three areas contribute more to one having rhetorical ability:
The significance of the debate is relevant to rhetorical pedagogy, since the kind and amount of rhetorical theory and practice must always be negotiated, and will always relate to the natural ability students come with.
While it is easy to attribute to Abraham Lincoln a kind of homespun genius, especially since his schooling was of a limited and unsophisticated nature, we would be better justified to attribute the success of "The Gettysburg Address" or his eloquent inaugural address to his long years of public oratory. Lincoln knew how to speak to a crowd because he'd been doing it for so long, and this practical experience taught him what would work in a given situation, and what would not.
Cicero, De Or. 1.25, 31-32, 48; 2.18-21; Quint. 2.11-12, 2.17-20 passim.