New York Times best-selling author Stephen Mansfield’s latest book is “Lincoln’s Battle With God.” A former pastor and radio show host, he’s written biographies on Winston Churchill, George Whitefield, President Obama, President George W. Bush and Booker T. Washington. Mansfield describes himself as a Christian and lives in both Nashville, Tenn., and Alexandria.

Your book describes Abraham Lincoln as a young atheist who eventually becomes a believer in God and an author of some of the most poetic theological statements we have in American political speeches. What were the key turning points in that transformation?